Jefferson, IA Weather

Key Messages

- Warm temperatures and dry conditions continue through Wednesday.

- Breezy conditions across northern northern and northwest Iowa Tuesday afternoon.

- Rain potential (20 to 30% chance) returns Saturday into Saturday night, mainly over northern and western Iowa.

Short Term

Issued at 243 AM CDT Tue Oct 20 2026

Current synoptic analysis places a strong Canadian high pressure near the Great Lakes, which remains the primary driver of our persistent dry pattern. A few diurnal clouds present earlier today have cleared, setting up strong radiational cooling overnight. Expect low temperatures this morning to dip into the lower 40s, with upper 30s possible across northern Iowa. Current guidance hints at patchy fog development late tonight; however, dew point depressions remaining around 2-3 degrees paired with light 5-6 mph surface wind should keep boundary layer mixing just sufficient enough to limit widespread dense fog.

For Today, boundary layer mixing and diurnal heating will allow temperatures to once again climb into the upper 60s to lower 70s. The primary feature of note across northern Iowa, especially northwest Iowa will be tightening surface pressure gradients as a mid level shortwave disturbance traverses the Rockies and emerges onto the plains. This will lead to gusty southerly winds reaching up to 20 mph Tuesday afternoon. Gusts will quickly subside toward sunset as we lose diurnal heating.

Wednesday

As we shift into Wednesday, the aforementioned shortwave disturbance will continue to propagate eastward across the region. Mid-level moisture advection ahead of the trough axis will yield a slight increase in cloud coverage. While a few guidance members show light/spotty showers across southwest Iowa, soundings reveal a substantial layer of dry air in the sub-cloud layer. Any precipitation will struggle to reach the ground due to low level evaporation (virga), keeping precipitation chances below 10%. Warm and dry conditions will otherwise persist.

Long Term

Issued at 129 PM CDT Mon Oct 19 2026

The aforementioned 500 mb ridging generally persists through the second half of the work week, keeping conditions dry and warm through at least Thursday. However, an approaching northern stream trough late this week will help release the western CONUS cutoff low that has been blocking our pattern thus far. This amplified troughing will progress eastward into the Rockies and Great Plains regions through the second half of the week, shoving the ridge and coincident surface high off eastward. The amplified flow pattern will bring a better fetch of moisture into at least the western half of the state Friday into Saturday although the main surface low and better synoptic forcing generally stays north and west of Iowa. Still, some rain/showers may develop along the trailing cold front expected to move into Iowa Saturday into Saturday night. These rain chances aren't overly high (around 20 to 30% per NBM) and heavily favor northwestern Iowa given quite a bit of uncertainty with how robust the boundary will be so far from the parent low. Even if the rain doesn't come to fruition, breezy conditions are likely to develop Friday and Saturday with the increased pressure gradients, again over northern and western Iowa. Cooler temperatures begin to fill in Sunday into Monday, although the magnitude of cooling will be dependent on how robust the cold front is on Saturday.

Aviation

Issued at 540 AM CDT Tue Oct 20 2026

Areas of patchy fog are present in a few spots this morning but should burn off after the sun rises. VFR conditions are expected to prevail one the fog burns off. Skies are expected to remain mostly clear throughout the day but clouds are expected to return by the end this TAF period.