Fall-like chill to spill into northern Illinois over the weekend

Radiational cooling is well underway, meaning temperatures fell rapidly overnight, leaving them close to the dew point temperature. 

What does this entail? A scenario like the past few mornings where patchy dense fog was able to develop ahead of the morning drive. This morning, we have a few locales reporting low visibility including Rochelle at 2-mile visibility and Janesville at .3-mile visibility. As always, give yourself extra travel time as changes in visibility will likely occur. 

The rest of the day will be problem-free as skies stay partly cloudy into the afternoon. With a more west-southwest wind in place, afternoon highs will hover on either side of the 80° mark. Towards the evening, clouds will increase as the first "fall" cold front of the season approaches from the northwest. With the additional cloud cover will come a low chance for a shower or storm. Otherwise, it will be the downward trend in temperatures that follows the frontal passage that will be the bigger headline.

Clouds will decrease prior to midday, leaving us with partly cloudy skies for Saturday afternoon. Despite a wind change to the northwest, we will still manage to warm into the upper 70s, close to 80°. The changes really don't arrive until Sunday where afternoon highs will be limited to the low 70s. Overnight lows Sunday will be flirting with the upper 40s.

The coolest air arrives early next week, leaving highs possibly in the upper 60s Monday. With high pressure sitting to our northwest, most of this stretch will end up dry, though we do keep a slim chance for a shower or storm Sunday and Monday. 

Overnight lows by the time Tuesday morning rolls around will end up in the upper 40s, then again by Wednesday morning. This may be cool enough for a light jacket. Temperatures from there will slowly climb as we approach Labor Day weekend, reaching the mid to upper 70s by next Thursday.