Marine Weather and Tide Forecast for Beloit, WI

UPDATE
Issued 646 AM CDT Sun Sep 20 2026

The Flood Watch will be allowed to expire at 7 AM CDT this morning for the southern portions of the forecast area. The lingering moderate to sometimes heavy rainfall rates over this area should continue to gradually taper off into this morning, and eventually move south of the area by midday or early afternoon. Will still watch for some urban and small stream flooding and river rises, but the increasing northeast winds should continue to help push back the northern edge of the rain into this morning, as well as helping to erode it.

Gusty northeast winds today into tonight are expected, becoming more east to northeast on Monday. Low clouds should linger this morning, before slowly rising this afternoon and tonight. There could be some breaks in the clouds tonight into Monday, though there should still be mostly cloudy skies. An advancing shortwave trough and lingering moisture aloft may help bring some showers into the area tonight into Monday night. Kept 20 to 30 percent chances in southern and western parts of the area for now. Temperatures should remain cool in the middle to upper 60s today and Monday.

The Beach Hazards Statement for a high swim risk will continue into Tuesday for the beaches along Lake Michigan, for gusty east to northeast winds and building waves of 5 to 11 feet. This may need to be extended into Wednesday night, as conditions may linger. These conditions will result in dangerous swimming conditions, so stay out of the water.

Wood

SHORT TERM
Issued 1112 PM CDT Sat Sep 19 2026

Current Overnight through Sunday Night:

A band of moderate rain is currently angled from Northern Dane County through Northern Racine County in association with lift from 925mb frontogenesis. Rainfall has been pretty efficient within this band, with 0.5 inch accumulations recorded within one hour. This band is generally pushing E-SE and should push out over Lake Michigan in a progressive manner over the next few hours.

Meanwhile, convection is currently blossoming south of the Wisconsin/Illinois border as WAA causes uplift over a sfc boundary. As the night goes on, high pressure from central Canada is expected build southward into the Upper Great Lakes, increasing the sfc pressure gradient and generating northeasterly flow, which will continue to keep the surface boundary south of the border. The compression of the environment between the high and the sfc boundary will also further intensify the convection over Illinois. It is projected that some of this convection will deal a glancing blow of rain to the southern Wisconsin Counties along the Wisconsin and Illinois border generally from 3am onward. While the heaviest rain will stay in Illinois, and additional inch to inch and a half of rain may occur during the early morning hours in these counties. A Flood Watch will stay out along the WI/IL border until 7am to account for the possibility of this rain overnight.

Rain should quickly end through the post dawn hours of the morning on Sunday as the influence of the high pressure continues to push into the upper Great Lakes region. By the mid to late afternoon, some breaks in the clouds may occur over east-central to south central Wisconsin. With the stronger pressure gradient over the region, wind gusts from 20 mph inland to 30mph near the lake will be possible.

The strong winds will drive high onshore waves and rip currents at all Lake Michigan beaches. A Beach Hazard Statement is in effect from now through Tuesday owing to the long duration hazards swimming conditions.

CMiller

LONG TERM
Issued 1148 PM CDT Sat Sep 19 2026

Monday through Friday:

High pressure will continue to linger over the northern Great Lakes Monday ahead of an approaching cutoff low over Iowa.
Chances for scattered rain (15 to 30% PoPs) will persist through the day as some moisture tries to work into the area from the cutoff low, but ultimately runs into the subsidence of the high. The cutoff low should lift back into the background zonal flow aloft Monday night into Tuesday and precip chances should largely end by Tuesday morning.

Dry conditions then look to be in store for the rest of the extended period. Some residual troughing aloft will keep us cool through the mid week period with highs in the low to mid 60s.
70s then return for the upcoming weekend as ridging begins to build over the upper MS Valley.

CMiller

AVIATION
Issued 646 AM CDT Sun Sep 20 2026

The lingering moderate to sometimes heavy rainfall over Madison and Milwaukee and terminals to the south should continue to gradually taper off into this morning, and eventually move south of this area by midday or early afternoon. The increasing northeast winds should continue to help push back the northern edge of the rain into this morning, as well as helping to erode it. There is some 1 to 4 mile visibility within the rain, with Milwaukee seeing locally lower values to 1/2 mile at times.
These should improve to greater than 6 miles once the rain moves out.

Gusty northeast winds today into tonight are expected, becoming more east to northeast on Monday. Low clouds with ceilings of 300 to 800 feet AGL should linger this morning, before slowly rising this afternoon above 1500 to 2500 feet AGL. They should rise above 3500 feet AGL tonight, though may drop back below 3000 feet AGL Monday morning. There could be some breaks in the clouds tonight into Monday.

Some showers may move into the area tonight into Monday night, but kept mention out of TAFs for now.

Wood

MARINE
Issued 646 AM CDT Sun Sep 20 2026

Low pressure around 29.8 inches will move from southeast Iowa into the Ohio Valley today into Monday. Meanwhile, high pressure around 30.4 inches will strengthen and move east into Ontario today into Monday, then into Quebec for Monday night into Wednesday. Gusty northeast winds are expected today into tonight, becoming east and remaining gusty Monday into Wednesday. A few gale force gusts may occur today into Monday, mainly over southern portions of the lake. Building waves are expected over western portions of the lake today into the middle of the week. Lighter easterly winds should then linger for Thursday into Friday, as the high pressure system slowly moves further east.

A Small Craft Advisory remains in effect into Tuesday evening for all of the nearshore waters of Lake Michigan. Gusty east to northeast winds and building waves of 5 to 11 feet are expected during this period. A few gale force gusts may occur today into Monday as well. The Small Craft Advisory may need to be extended into Wednesday night, as winds and waves may remain high enough.

Wood

MKX WATCHES/WARNINGS/ADVISORIES
WI
Beach Hazards Statement
WIZ052-WIZ060-WIZ066-WIZ071-WIZ072 until 7 PM Tuesday.

Flood Watch...WIZ062-WIZ063-WIZ064-WIZ065-WIZ066-WIZ067-WIZ068- WIZ069-WIZ070-WIZ071-WIZ072 until 7 AM Sunday.

LM
Small Craft Advisory
LMZ643-LMZ644-LMZ645-LMZ646 until 7 PM Tuesday.