Monona, WI Weather

Key Messages

- Dense fog has formed over east-central WI and is slowly spreading southward into tonight. Dense Fog Advisory already in effect for Sheboygan County. Expansions of the Advisory further south are possible later tonight.

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

- Temperatures closer to normal early next week, followed by a return to warmer weather midweek.

Short Term

Issued 1030 PM CDT Fri Oct 23 2026

Tonight through Saturday night:

Light southeasterly winds and lingering humidity over Lake MI have formed a bank of fog and low stratus clouds drifting into Sheboygan county and points north. METARS and DOT cameras confirm the fog is dense in Sheboygan County, and a Dense Fog Advisory will remain in effect through 9 AM Saturday morning (unless trends warrant a change). An expansion of this Advisory southward into Washington and Ozaukee counties later tonight is possible, given GOES Night Fog RGB composites and surface observations are beginning to indicate a southward creep to the fog over time, mainly along and east of the Kettle Moraine hills. We could even see this fog continue south into the MKE metro late tonight, though forecast confidence is low.

The combination of continued airflow at the surface, abundant high- altitude cloud cover, and weak terrain-locking of the Kettle Moraine hills should prevent any fog formation further inland. From a Fond du Lac to Walworth line westward, looking fog free for tonight at this time.

Into post-dawn Saturday morning, winds turn due south and accelerate slightly, clearing away any lingering fog. Additional periods of broken high-altitude cloud cover are anticipated through Saturday and Saturday night, but dry weather continues all the same. Highs in the low 70s expected inland; some shoreline ventilation (SSE winds) could hold highs to the mid 60s for far eastern WI.

Sheppard

Long Term

Issued 1030 PM CDT Fri Oct 23 2026

Sunday through Friday:

Low pressure tracking east across Hudson Bay Canada this weekend will drag a cold front into WI. The front should reach northwestern portions of WI by late Saturday night into Sunday morning, with strong high pressure over Saskatchewan then forcing the front across southern WI later Sunday through Sunday night. Predominantly dry weather is expected to accompany the frontal passage, and the late arrival of the front allows daytime highs to reach the low 70s Sunday. CAA behind the front kicks in late Sunday night into Monday, with northeasterly winds off the lake. As such, central and eastern WI are forecast to observe highs in the 50s, with highs in the mid 60s further west along the southern edge of the state.

Meanwhile on Monday, a 500mb shortwave trough will dig into the central Great Plains, phasing with the aforementioned frontal boundary to seed surface low pressure. This low pressure looks to lift northeast into Monday night, bringing some 5-15% rain chances to the CWA. The bulk of the QPF and higher precip chances with this system land in MN and northwestern WI, leaving us predominantly dry as it passes. The remnant baroclinic zone from that activity then sets the stage for an additional upper trough and surface low to slide northeast from the Plains midweek. The placement of precip with this second system is less certain, but could track through the same corridor of MN / NW-WI or further east. ~15-30% precip chances are forecast for the CWA Wednesday until ensembles converge on a system track. In any scenario, we will be in the warm sector of both passing systems, resulting in a warming trend towards midweek.

This same pattern looks to continue later this week, with additional rain chances.

Sheppard

Aviation

Issued 1030 PM CDT Fri Oct 23 2026

Dense fog and low stratus clouds (persistent LIFR) have formed over Sheboygan County and points north as light southeast surface winds advect humid air onshore. This activity is likely to persist through around daybreak Saturday morning, and could (potentially) spread further south overnight, mainly for areas east of the Kettle Moraine hills, potentially to KMKE and KRAC (lower potential but still can't rule out KENW). Satellite signatures and surface observations show that the southward creep (from Sheboygan into Ozaukee and Washington county) is underway, and if it persists, MKE TAF may require an amendment to add fog potential late tonight into early Saturday morning.

Further inland, broken high-altitude clouds and continued southeasterly winds should prevent fog formation.

Winds turn due south into Saturday and become breezy, removing the fog within a few hours after sunrise. Periods of high- altitude clouds continue to roll through Saturday and Saturday night, but dry weather and VFR is anticipated.

Sheppard