Marine Weather and Tide Forecast for Zion, IL

DISCUSSION
Issued at 130 PM CDT Mon May 25 2026

A broad surface high continues to reside over the southern Great Lakes and northern Ohio River Valley this afternoon. As a result, sunny skies are being seen across the area with temperatures to warm into the lower to mid-80s this afternoon.
While there is a shortwave disturbance pivoting across southern WI and northern IL, the earlier rain showers associated with it continue to weaken as the system encounters drier air. Though, a period of partly to mostly cloudy skies is expected for our northern tier of counties for a few hours this afternoon.

Heading into this evening, a weak lake breeze will ooze onshore in northeast IL which will result in quickly cooling temperatures towards the 60s there. Otherwise, expect mostly clear conditions tonight aside from some high cirrus lifting northward from the broad area of showers and thunderstorms along the Gulf Coast. Overnight lows will bottom out in the upper 50s and lower 60s. Tuesday will feature similar conditions to today with highs once again in the mid-80s with slightly cooler conditions (mid-70s) near the lake due to another lake breeze.
Though, increasing cloud cover is expected on Tuesday and Tuesday night which will aid in keeping nighttime lows a couple degrees warmer in the lower to mid-60s.

While we enjoy the tranquil weather on Tuesday, a broad upper trough will begin to dig into the northeast CONUS. At the same time, the upper low off the Pacific Northwest will also begin to dig into the southwest CONUS which in turn will begin to eject the weak shortwave causing the showers/storms near the Gulf northward towards IL and IN on Wednesday. Given that most of northern IL and northwest IN will still be under the influence of an elongated ridge, it seems that the bulk of the aforementioned showers and storms lifting towards the area should stay more into central IL and IN. Therefore, another mostly dry day is expected for Wednesday but an isolated shower or storm (20% chance) cannot be ruled out near and south of US-24. Furthermore, there will also be a cold front diving southward out of WI Wednesday afternoon and evening which could also bring a few showers/storms to portions of northern IL.
However, with forecast soundings looking somewhat dry and the better forcing with the upper trough forecast to be more into MI, it seems the coverage of any showers/storms with the front will be very hit and miss especially with southward extent. So while the official forecast does have some 20-30% POPs near the IL-WI line there is a chance that most of these areas remain dry.

Regardless, temperatures will quickly cool behind the front as north-northeast winds usher in cooler air. With the front's later arrival (current forecast is for fropa to occur late afternoon) highs on Wednesday should still get into the lower to mid-80s (upper 60 near the lake), but if the front arrives quicker than expected temperatures could verify much cooler. In addition to the cooling temperatures, winds behind the front also look to become breezy with gusts around 20-25 mph. These north-northeast winds will allow waves to build on Lake Michigan and result in rip currents and dangerous swimming conditions at IL and northwest IN beaches.

High pressure is expected to build back into the Great Lakes Wednesday night through weeks end which will result in dry and tranquil weather conditions. Though, persistent northeast winds do look to keep temperatures more in the seasonable range with daily highs in the upper 70s to lower 80s (60s near the lake), especially on Thursday, and overnight lows in the 50s through next weekend.

Yack

AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/
Issued at 1233 PM CDT Mon May 25 2026

Aviation concerns for the 18Z TAFs:

- Lake breeze wind shift to SE at ORD/MDW mid-late afternoon, and again Tuesday afternoon.

- Mid-level VFR deck will affect mainly RFD this afternoon/early evening, though isolated high-based SHRA expected to remain N/NW of the airport.

Elongated surface high pressure ridge axis stretches from Missouri northeast to Lake Erie at midday. North of the ridge axis, surface winds were generally light (<10 kts) from the south-southwest. Within this light gradient, a southeasterly lake breeze is expected to develop this afternoon and bring southeast wind shifts to ORD and MDW in the 20-22Z time frame.
Winds will likely remain south-southeast for ORD/MDW for a good portion of the night (as well as other sites after sunset this evening), before becoming light south-southwest again Tuesday morning. Another lake breeze is expected Tuesday afternoon, with current high-res wind guidance suggesting a slightly earlier wind shift to southeast for ORD/MDW than today.

Otherwise, a weak mid-level wave will track east across the area into this evening. The main impact will be SCT-BKN VFR mid-level clouds in the 10-12 kft range. RFD will be most likely to see BKN bases with this, as wave is moving into drier/less favorable air mass farther to the east for maintaining cloud cover.
Spotty high-based SHRA over southwest WI/northeast IA also are expected to weaken/dissipate with no impacts to the terminals.

Ratzer

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...None.