After a couple of mild and rather humid days for early October, the transition to a fall-like chill has begun and will be around eastern Iowa through the upcoming weekend.
The pattern which featured southwesterly flow the last several days with warm, humid air that fueled numerous rain chances will switch to a generally northwest flow with colder, drier Canadian air punching in. That will cutoff the moisture supply as the jet stream buckles south.
High pressure will dig in and influence the weather Thursday and Friday. Temperatures Friday morning will be in the 30s with some upper 20s possible in far northeast Iowa. That will lead to some possible widespread frost.
A clipper system will track through the region Friday with the chance of a light shower or sprinkles mainly south of Highway 20. However, moisture will be rather meager and chances are small. It will be another chilly day with high temperatures stuck in the 40s.
Temperatures will remain well below normal through the weekend, but it will be a dry and quiet. Two storms will bisect the area on Saturday, one to the north and the other south. As a result, winds will briefly turn to the southwest as temperatures get a bump into the 50s.
High pressure settles back in on Sunday with high's cooler in the 40s. Night lows will be cold in the 30s with again areas of frost likely.
The month of October usually brings the first Fall Freeze and Hard Freeze to eastern Iowa.
The Fall Freeze is a minimum temperature of 32 degrees and Hard Freeze, also known as the "killing" freeze because it signals the end of the growing season, is a minimum temperature of 28 degrees.