Delavan, WI Weather

Key Messages

- Fog possible tonight & Thursday evening/night.

- Above normal temperatures & rain-free conditions continue into the weekend.

- Temperatures trending back toward normal next week, with chances for rain Monday night into Tuesday and Wednesday night.

Update

Issued 616 PM CDT Wed Oct 21 2026

Generally quiet weather will continue through the evening and overnight hours under high pressure. Still looks like some fog will be possible later tonight into early Thursday. Overall, the forecast is on track through tonight, with no significant updates anticipated.

DDV

Short Term

Issued 140 PM CDT Wed Oct 21 2026

This Afternoon through Saturday Night:

Synopsis/Mesoanalysis: High pressure is centered along the North Dakota-Manitoba border this afternoon, with a cold front extending from Quebec toward the northern Lake Superior vicinity. Positioning of the features is allowing for light southwesterly breezes to become established across southern Wisconsin. Combined with abundant sunshine, the breezes are allowing temperatures to climb quickly toward the 70 degree mark as of the 1 PM CDT hour. Anticipate that temps will continue to climb into the low-mid 70s by mid-afternoon under persisting mostly sunny skies. Mid-upper level ridging will build into the Missouri Valley tonight, allowing the aforementioned area of high pressure to broaden in size. Expansion of the high will whittle away at the leading cold front, with only a non- baroclinic, northerly wind shift left by daybreak. The wind shift will work through the area Thursday as high pressure moves directly overhead. Proximity of the high & affiliated light/variable winds will support periods of fog potential both tonight & Thursday evening/night. Southwest winds will quickly return as the high departs east on Friday, maintaining above normal high temperatures into the weekend.

Tonight: Will be monitoring for areas of fog development as high pressure builds in from the Northern Plains. Extent---as well as density---of any fog will be highly sensitive to low level wind speeds, which remain uncertain given southern Wisconsin's positioning on the southeast flank of the building high & within the affiliated surface pressure gradient. If full decoupling of the boundary layer can occur, deeper moisture returns arriving on the heels of this afternoon's southwesterly winds could be supportive of some dense fog. Will be monitoring visibility trends through the overnight hours & issuing any headlines should conditions warrant. Slow down, use low beam headlights, and allow for extra following distance if encountering fog on the roads.

Thursday Evening & Night: Will be watching for additional, more advection-based fog as passing high pressure & affiliated east- northeast flow draw a marine air mass inland from Lake Michigan. Similar to tonight, it remains too early to tell if any fog could be dense. Will be monitoring trends over coming forecast updates.

Quigley

Long Term

Issued 140 PM CDT Wed Oct 21 2026

Sunday through Wednesday:

Synopsis: Above normal temperatures will continue to prevail during the day Sunday as a slow-moving cold front drifts into northern Wisconsin. With frontal forcing remaining well-removed from the region, dry conditions are currently expected along with the warm temperatures. Moving into next week, global ensemble guidance is in general agreement for 1) an upper shortwave passage during the Monday-Tuesday timeframe and 2) the arrival of a larger-scale upper trough and surface frontal push by the middle of the week/conclusion of the long term period. Northerly surface mass responses affiliated with the early week shortwave will help shove the Sunday cold front through southern Wisconsin on Monday, bringing more seasonable temperatures to the area through the first half of next week. Rain chances return to the forecast during the passage of both perturbations, with Monday night into Tuesday & Wednesday night into Thursday currently favored for the most widespread activity. Thunderstorm chances appear low at this time.

Monday through Wednesday: Have largely maintained an NBM forecast through this portion of the period given ensemble agreement regarding synoptic pattern evolution. Said forecast pulls high temperatures back into the mid-50s to low-60s, in addition to bringing chance (~25-40%) precip probabilities to the region Monday night/Tuesday and Wednesday night. Barring changes in consistency across the global ensemble suite, would anticipate general stability in this forecast into this weekend. Will continue to monitor for any possible changes over coming updates.

Quigley