Marine Weather and Tide Forecast for Chicago, IL
 | Sunrise 5:14 AM Sunset 8:30 PM Moonrise 1:53 AM Moonset 4:33 PM |
LMZ742 Expires:202506212145;;130744 Fzus53 Klot 211426 Nshlot
nearshore marine forecast national weather service chicago/romeoville il 926 am cdt Sat jun 21 2025
for waters within five nautical miles of shore on lake michigan
waves are provided as a range of significant wave heights, which is the average of the highest 1/3 of the waves, along with the average height of the highest 10 percent of the waves which will occasionally be encountered.
lmz740>744-212145- winthrop harbor to wilmette harbor il- wilmette harbor to northerly island il- northerly island to calumet harbor il- calumet harbor il to gary in-gary to burns harbor in- 926 am cdt Sat jun 21 2025
.gale warning in effect through this evening - .
Rest of today - Southwest gales to 35 kt. Mostly Sunny. Waves 2 to 4 ft.
Tonight - Southwest gales to 35 kt diminishing to 15 to 25 kt. Clear. Waves 2 to 4 ft subsiding to 1 to 3 ft.
Sunday - Southwest winds 15 to 25 kt increasing to 30 kt. Sunny. Waves 1 to 3 ft.
Sunday night - South winds 15 to 25 kt becoming southwest 15 to 20 kt. Clear. Waves 1 to 3 ft.
nearshore marine forecast national weather service chicago/romeoville il 926 am cdt Sat jun 21 2025
for waters within five nautical miles of shore on lake michigan
waves are provided as a range of significant wave heights, which is the average of the highest 1/3 of the waves, along with the average height of the highest 10 percent of the waves which will occasionally be encountered.
lmz740>744-212145- winthrop harbor to wilmette harbor il- wilmette harbor to northerly island il- northerly island to calumet harbor il- calumet harbor il to gary in-gary to burns harbor in- 926 am cdt Sat jun 21 2025
LMZ700
No data
No data
7 Day Forecast for Marine Location Near Chicago, IL
NEW! Add second zone forecast
FXUS63 KLOT 211134 AFDLOT
Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 634 AM CDT Sat Jun 21 2025
KEY MESSAGES
- First heat wave of the summer begins today and will continue into next week. Expect multiple days of highs well into the 90s and peak afternoon heat indices of around 105F.
- Extreme Heat Warning remains in effect for the city of Chicago and Cook Co. where special 3-day Extreme Heat Warning criteria of peak heat indices of 100F+ are expected to be reached.
- Heat Advisory remains in effect for the rest of the area today-Monday. Some areas may need to be upgraded to an Excessive Heat Warning if Tuesday again has ~105F heat indices.
- Today will be unusually windy into early evening given the heat, with southwesterly gusts up to 35-45 mph I-80 and north and up to 30-35 mph south of I-80.
DISCUSSION
Issued at 307 AM CDT Sat Jun 21 2025
Through Sunday:
Today ushers in the first heat wave of the season. This morning, a pronounced upper ridge is building over the region as a center of high pressure aloft strengthens and scoots into the middle Mississippi Valley shunting the polar jet well to our north. This will allow for a constant feed of hot, moist air into the region over the next few days bringing oppressive heat and humidity to this weekend and early next week.
Today is already off to a warm start with temperatures expected to be sitting in the lower and middle 70s at daybreak.
Conditions will then quickly heat up through the morning with temperatures expected to approach 90 degrees by the end of the morning and max out in the lower and middle 90s this afternoon.
There remains some uncertainty in dewpoint trends into the afternoon, and a few degree Td difference will mean up to a several degree difference in expected heat index. A few of the traditionally mixier model camps suggest we could mix dewpoints down into the lower 70s this afternoon. While we would normally be tempted to favor these drier solutions on a hot day like today, continued to lean more toward the mean of our higher-res models which puts dews in the middle 70s. This places the afternoon heat index forecast in the 100-105F range, possibly higher locally. We'll probably find that dewpoints mix out slightly more efficiently in and around Chicago, which may allow for highs to tap into the upper 90s near the city. And with offshore winds today, this heat will be felt all the way up to the lakeshore.
Conditions will remain warm and muggy through the night with overnight lows only forecast to drop into the middle and upper 70s. It's likely that in and around the city, the temperature will fail to fall below 80 tonight. This will make it very difficult for those without air conditioning or other effective means of cooling off to do so tonight before the extreme heat returns for Sunday. Sunday will feel very similar to today.
Temperatures are expected to be a tad warmer although dewpoints look a tad cooler during the day. So this should balance out any major changes to heat index expectations with 100-105F again looking likely Sunday afternoon.
No changes have been made to the going heat headlines. An Extreme Heat Warning goes into effect for Cook County this morning and lasts through Monday for the likelihood of at least three consecutive days of heat indices >100F. While such conditions are expected outside of Cook County as well, a reminder that this is a Warning threshold for the particularly vulnerable Cook County. For the remainder of the area, a Heat Advisory is in effect from this morning through Monday.
An important facet of the forecast today will be the wind. A low level jet is currently in the process of strengthening overhead along a tightening pressure gradient. The KLOT VWP has recently been sampling 45 kt of flow at 2 kft AGL, which equates to roughly 925mb. Gusts are already pushing 25 to at times 30 mph and they should quickly build, and become much more frequent, as soon as the boundary layer opens up after sunrise.
Gusts during the afternoon and early evening are expected in the 35 to 45 mph range. The highest winds should be found near and north of I-80 where the strongest low level flow will track.
While occasional gusts greater than 45 mph are certainly possible, don't think this will be a frequent-enough occurrence to consider a Wind Advisory at this time. Do not expect these winds to provide relief from the heat today. It's important to know that there comes a point in extreme heat when a strong breeze no longer helps cool the body and actually has an opposite effect; think using a hair dryer on low vs high. So these winds may actually make the heat feel overall more oppressive. Conditions will remain breezy this evening and tonight with more 30+ mph gusts likely on Sunday, again with the strongest winds expected near and north of I-80.
Doom
Sunday Night through Friday:
The oppressive heat over the weekend is set to continue into Monday as the pronounced mid-upper ridge remains established over the region. Forecast vertical profiles Monday afternoon suggest deeper mixing above 850mb could support triple digit temperatures being achieved in some spots given continued warm 850mb temps (20-22C per 0Z GEFS/EPS). For now have capped high temperatures at 99, warmest in Chicago. In tandem, lower dew points in the mid 60s should help keep heat indices relatively in check (but still very warm!), in the 100-105 degree range.
While this may not end up meeting true "heat advisory" criteria (>=105F) in some areas, the prolonged nature of the heat wave supports maintaining heat headlines through at least Monday.
The upper ridge will begin to flatten out late Monday into Tuesday with surface high pressure becoming established over northern Minnesota helping to shift a surface cold front closer to the area. At this range it looks like any shower/storm activity along the boundary will remain mainly northwest of the local area across Iowa into Wisconsin but a stray shower/storm can't be ruled out into northwest Illinois Monday night. There remains some variability with where this boundary ultimately stalls out into Tuesday. At this range it could end up over northern Illinois but potentially still as far north as Wisconsin. A further north scenario could lead to a fourth consecutive day of oppressive heat and accordingly an extension of heat headlines, especially south of I-80. Stay tuned!
With all that said, we plan to continue messaging that while this sort of heat is not unusual to see during a given summer, a proactive approach to protecting yourself and others from the heat this weekend into early next week is very much warranted.
This is due to the combination of the following:
1. This being the first heat wave of the season following a relatively cool end to spring.
2. The prolonged nature of the heat (potentially > 3 days for some).
3. Warm overnight lows in the mid-upper 70s (~80 in Chicago)
will lead to little relief from the heat, especially for those without air conditioning.
As the aforementioned surface high expands eastward across Ontario midweek the surface front begins to shift more solidly into northern Illinois. This will serve as the focus for periodic shower and storm chances (20-50%) through the end of the week as weaker disturbances move overhead along the quasi- zonal flow. The northern periphery (and stronger mid-level flow)
appears to remain well north of the area, nevertheless, can't rule out strong to severe storm clusters/MCSs moving through the broader region during this timeframe.
Petr
AVIATION /12Z TAFS THROUGH 18Z SUNDAY/
Issued at 630 AM CDT Sat Jun 21 2025
- Strong SSW winds are expected today with gusts in the 30-35 kt range (highest in the afternoon).
Winds are expected to steadily increase through the morning out of the south southwest with gusts in the 30-35 kt range developing by mid morning and lasting through early evening. A brief period of near 40kt gusts also can't be ruled out late in the afternoon. Winds begin to ease toward sunset (~0130Z)
leading to another round of potential low-level wind shear concerns overnight beneath a 45-50kt low-level jet. Expect another breezy day again on Sunday, though not quite as windy as today (25-30kt range).
Petr
MARINE
Issued at 307 AM CDT Sat Jun 21 2025
A Gale Warning is now in effect for the Illinois nearshore waters and the Indiana nearshore waters from Calumet Harbor to Burns Harbor from 7 AM to 10 PM today.
We're expecting strong south-southwest winds to quickly increase after daybreak due to a tight pressure gradient across the region. Hot temperatures and deep mixing on land but the stabilizing influence of the still cool lake waters will result in the strongest winds likely being confined to the first couple miles or so of the nearshore.
Confidence is highest in gale force speeds/frequent gale force gusts to around 35 kt in the Gale Warning area, with a bit lower confidence from Burns Harbor to Michigan City. We may need to consider expanding the warning if confidence in frequent gales increases for this nearshore zone.
If hazardous winds for small boats don't persist through tonight, they're expected to redevelop on Sunday, with a similar process repeated into Monday.
Castro
CLIMATE
Issued at 114 PM CDT Thu Jun 19 2025
Temperatures this weekend into early next week could potentially threaten record highs and record warm lows for Chicago and Rockford.
Here are the current records:
Chicago High Warm Low Saturday 6/21 101 (1988) 74 (1923)
Sunday 6/22 97 (1988) 76 (1923)
Monday 6/23 97 (1930) 79 (1923)
Rockford High Warm Low Saturday 6/21 100 (2022) 71 (1995)
Sunday 6/22 97 (1923) 73 (1908)
Monday 6/23 97 (1923) 74 (1908)
NWS Chicago
LOT WATCHES/WARNINGS/ADVISORIES
IL...Heat Advisory from 10 AM this morning to midnight CDT Monday night for ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010- ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032- ILZ033-ILZ039-ILZ106-ILZ107-ILZ108.
Extreme Heat Warning from 10 AM this morning to midnight CDT Monday night for ILZ103-ILZ104-ILZ105.
IN...Heat Advisory from 10 AM CDT /11 AM EDT/ this morning to midnight CDT /1 AM EDT/ Monday night for INZ001-INZ002- INZ010-INZ011-INZ019.
LM...Gale Warning until 10 PM CDT this evening for Winthrop Harbor IL to Burns Harbor IN.
Small Craft Advisory until 10 PM CDT this evening for Burns Harbor to Michigan City IN.
Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 634 AM CDT Sat Jun 21 2025
KEY MESSAGES
- First heat wave of the summer begins today and will continue into next week. Expect multiple days of highs well into the 90s and peak afternoon heat indices of around 105F.
- Extreme Heat Warning remains in effect for the city of Chicago and Cook Co. where special 3-day Extreme Heat Warning criteria of peak heat indices of 100F+ are expected to be reached.
- Heat Advisory remains in effect for the rest of the area today-Monday. Some areas may need to be upgraded to an Excessive Heat Warning if Tuesday again has ~105F heat indices.
- Today will be unusually windy into early evening given the heat, with southwesterly gusts up to 35-45 mph I-80 and north and up to 30-35 mph south of I-80.
DISCUSSION
Issued at 307 AM CDT Sat Jun 21 2025
Through Sunday:
Today ushers in the first heat wave of the season. This morning, a pronounced upper ridge is building over the region as a center of high pressure aloft strengthens and scoots into the middle Mississippi Valley shunting the polar jet well to our north. This will allow for a constant feed of hot, moist air into the region over the next few days bringing oppressive heat and humidity to this weekend and early next week.
Today is already off to a warm start with temperatures expected to be sitting in the lower and middle 70s at daybreak.
Conditions will then quickly heat up through the morning with temperatures expected to approach 90 degrees by the end of the morning and max out in the lower and middle 90s this afternoon.
There remains some uncertainty in dewpoint trends into the afternoon, and a few degree Td difference will mean up to a several degree difference in expected heat index. A few of the traditionally mixier model camps suggest we could mix dewpoints down into the lower 70s this afternoon. While we would normally be tempted to favor these drier solutions on a hot day like today, continued to lean more toward the mean of our higher-res models which puts dews in the middle 70s. This places the afternoon heat index forecast in the 100-105F range, possibly higher locally. We'll probably find that dewpoints mix out slightly more efficiently in and around Chicago, which may allow for highs to tap into the upper 90s near the city. And with offshore winds today, this heat will be felt all the way up to the lakeshore.
Conditions will remain warm and muggy through the night with overnight lows only forecast to drop into the middle and upper 70s. It's likely that in and around the city, the temperature will fail to fall below 80 tonight. This will make it very difficult for those without air conditioning or other effective means of cooling off to do so tonight before the extreme heat returns for Sunday. Sunday will feel very similar to today.
Temperatures are expected to be a tad warmer although dewpoints look a tad cooler during the day. So this should balance out any major changes to heat index expectations with 100-105F again looking likely Sunday afternoon.
No changes have been made to the going heat headlines. An Extreme Heat Warning goes into effect for Cook County this morning and lasts through Monday for the likelihood of at least three consecutive days of heat indices >100F. While such conditions are expected outside of Cook County as well, a reminder that this is a Warning threshold for the particularly vulnerable Cook County. For the remainder of the area, a Heat Advisory is in effect from this morning through Monday.
An important facet of the forecast today will be the wind. A low level jet is currently in the process of strengthening overhead along a tightening pressure gradient. The KLOT VWP has recently been sampling 45 kt of flow at 2 kft AGL, which equates to roughly 925mb. Gusts are already pushing 25 to at times 30 mph and they should quickly build, and become much more frequent, as soon as the boundary layer opens up after sunrise.
Gusts during the afternoon and early evening are expected in the 35 to 45 mph range. The highest winds should be found near and north of I-80 where the strongest low level flow will track.
While occasional gusts greater than 45 mph are certainly possible, don't think this will be a frequent-enough occurrence to consider a Wind Advisory at this time. Do not expect these winds to provide relief from the heat today. It's important to know that there comes a point in extreme heat when a strong breeze no longer helps cool the body and actually has an opposite effect; think using a hair dryer on low vs high. So these winds may actually make the heat feel overall more oppressive. Conditions will remain breezy this evening and tonight with more 30+ mph gusts likely on Sunday, again with the strongest winds expected near and north of I-80.
Doom
Sunday Night through Friday:
The oppressive heat over the weekend is set to continue into Monday as the pronounced mid-upper ridge remains established over the region. Forecast vertical profiles Monday afternoon suggest deeper mixing above 850mb could support triple digit temperatures being achieved in some spots given continued warm 850mb temps (20-22C per 0Z GEFS/EPS). For now have capped high temperatures at 99, warmest in Chicago. In tandem, lower dew points in the mid 60s should help keep heat indices relatively in check (but still very warm!), in the 100-105 degree range.
While this may not end up meeting true "heat advisory" criteria (>=105F) in some areas, the prolonged nature of the heat wave supports maintaining heat headlines through at least Monday.
The upper ridge will begin to flatten out late Monday into Tuesday with surface high pressure becoming established over northern Minnesota helping to shift a surface cold front closer to the area. At this range it looks like any shower/storm activity along the boundary will remain mainly northwest of the local area across Iowa into Wisconsin but a stray shower/storm can't be ruled out into northwest Illinois Monday night. There remains some variability with where this boundary ultimately stalls out into Tuesday. At this range it could end up over northern Illinois but potentially still as far north as Wisconsin. A further north scenario could lead to a fourth consecutive day of oppressive heat and accordingly an extension of heat headlines, especially south of I-80. Stay tuned!
With all that said, we plan to continue messaging that while this sort of heat is not unusual to see during a given summer, a proactive approach to protecting yourself and others from the heat this weekend into early next week is very much warranted.
This is due to the combination of the following:
1. This being the first heat wave of the season following a relatively cool end to spring.
2. The prolonged nature of the heat (potentially > 3 days for some).
3. Warm overnight lows in the mid-upper 70s (~80 in Chicago)
will lead to little relief from the heat, especially for those without air conditioning.
As the aforementioned surface high expands eastward across Ontario midweek the surface front begins to shift more solidly into northern Illinois. This will serve as the focus for periodic shower and storm chances (20-50%) through the end of the week as weaker disturbances move overhead along the quasi- zonal flow. The northern periphery (and stronger mid-level flow)
appears to remain well north of the area, nevertheless, can't rule out strong to severe storm clusters/MCSs moving through the broader region during this timeframe.
Petr
AVIATION /12Z TAFS THROUGH 18Z SUNDAY/
Issued at 630 AM CDT Sat Jun 21 2025
- Strong SSW winds are expected today with gusts in the 30-35 kt range (highest in the afternoon).
Winds are expected to steadily increase through the morning out of the south southwest with gusts in the 30-35 kt range developing by mid morning and lasting through early evening. A brief period of near 40kt gusts also can't be ruled out late in the afternoon. Winds begin to ease toward sunset (~0130Z)
leading to another round of potential low-level wind shear concerns overnight beneath a 45-50kt low-level jet. Expect another breezy day again on Sunday, though not quite as windy as today (25-30kt range).
Petr
MARINE
Issued at 307 AM CDT Sat Jun 21 2025
A Gale Warning is now in effect for the Illinois nearshore waters and the Indiana nearshore waters from Calumet Harbor to Burns Harbor from 7 AM to 10 PM today.
We're expecting strong south-southwest winds to quickly increase after daybreak due to a tight pressure gradient across the region. Hot temperatures and deep mixing on land but the stabilizing influence of the still cool lake waters will result in the strongest winds likely being confined to the first couple miles or so of the nearshore.
Confidence is highest in gale force speeds/frequent gale force gusts to around 35 kt in the Gale Warning area, with a bit lower confidence from Burns Harbor to Michigan City. We may need to consider expanding the warning if confidence in frequent gales increases for this nearshore zone.
If hazardous winds for small boats don't persist through tonight, they're expected to redevelop on Sunday, with a similar process repeated into Monday.
Castro
CLIMATE
Issued at 114 PM CDT Thu Jun 19 2025
Temperatures this weekend into early next week could potentially threaten record highs and record warm lows for Chicago and Rockford.
Here are the current records:
Chicago High Warm Low Saturday 6/21 101 (1988) 74 (1923)
Sunday 6/22 97 (1988) 76 (1923)
Monday 6/23 97 (1930) 79 (1923)
Rockford High Warm Low Saturday 6/21 100 (2022) 71 (1995)
Sunday 6/22 97 (1923) 73 (1908)
Monday 6/23 97 (1923) 74 (1908)
NWS Chicago
LOT WATCHES/WARNINGS/ADVISORIES
IL...Heat Advisory from 10 AM this morning to midnight CDT Monday night for ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010- ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032- ILZ033-ILZ039-ILZ106-ILZ107-ILZ108.
Extreme Heat Warning from 10 AM this morning to midnight CDT Monday night for ILZ103-ILZ104-ILZ105.
IN...Heat Advisory from 10 AM CDT /11 AM EDT/ this morning to midnight CDT /1 AM EDT/ Monday night for INZ001-INZ002- INZ010-INZ011-INZ019.
LM...Gale Warning until 10 PM CDT this evening for Winthrop Harbor IL to Burns Harbor IN.
Small Craft Advisory until 10 PM CDT this evening for Burns Harbor to Michigan City IN.
| Stations | Dist | Age | Wind | Air | Water | Waves | inHg | DewPt |
| CNII2 | 1 mi | 46 min | SSW 12G | 88°F | 70°F | |||
| 45198 | 4 mi | 26 min | SW 19G | 80°F | 62°F | 2 ft | 29.85 | 67°F |
| OKSI2 | 4 mi | 136 min | WNW 2.9G | 89°F | ||||
| CHII2 - Chicago, IL | 5 mi | 46 min | SW 40G | 89°F | 77°F | |||
| CMTI2 - 9087044 - Calumet, IL | 9 mi | 46 min | S 17G | 87°F | 29.83 | 74°F | ||
| 45174 | 20 mi | 36 min | WSW 16G | 79°F | 2 ft | 29.89 | ||
| BHRI3 - Burns Harbor, IN | 28 mi | 36 min | SSW 11G | 87°F | 29.89 | |||
| 45186 | 37 mi | 26 min | WSW 18G | 82°F | 60°F | 2 ft | ||
| MCYI3 - Michigan City, IN | 37 mi | 46 min | S 18G | 86°F | 29.83 | 76°F | ||
| WHRI2 - Waukegan Harbor, IL | 37 mi | 76 min | SSW 11G | 86°F | ||||
| 45187 | 45 mi | 26 min | WNW 16G | 78°F | 54°F | 2 ft |
Wind History for Calumet Harbor, IL
toggle option: (graph/table)
| Airport | Dist | Age | Wind kt | Vis | Sky | Weather | Air | DewPt | RH | inHg |
| KMDW CHICAGO MIDWAY INTL,IL | 9 sm | 22 min | SW 18G31 | 10 sm | Mostly Cloudy | 91°F | 72°F | 53% | 29.85 | |
| KORD CHICAGO O'HARE INTL,IL | 18 sm | 24 min | SW 19G34 | 10 sm | Partly Cloudy | 90°F | 73°F | 59% | 29.84 | |
| KGYY GARY/CHICAGO INTL,IN | 19 sm | 30 min | SW 08G26 | 10 sm | Clear | 93°F | 77°F | 60% | 29.87 | |
| KIGQ LANSING MUNI,IL | 22 sm | 20 min | SW 21G28 | 10 sm | Partly Cloudy | 90°F | 75°F | 63% | 29.89 | |
| KPWK CHICAGO EXECUTIVE,IL | 24 sm | 23 min | SW 16G28 | 10 sm | A Few Clouds | 91°F | 73°F | 56% | 29.85 |
Link to 1 hour of 5 minute data for KMDW
Terminal Aerodrome Forecast (TAF) for KMDW
Wind History Graph: MDW
(wind in knots)
GEOS Local Image of Midwest
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Chicago, IL,
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