Above average temperatures and warmth has been the rule of thumb not only the past few weeks, but the past few months. Its already the second week of November, and we still haven't had our first freeze in Rockford. The coldest temperatures have fallen was 35°, that we hit the 13th and 14th of October, but so far we haven't fallen below.
But, that is forecast to chance by the end of the work week. We're eyeing a cold front currently situated near Canada and the Pacific Northwest that will help to usher in colder air at the surface. Not only that, but a pattern shift in the upper levels of the atmosphere will also bring reinforced cold air. A large and amplified ridge of high pressure will bring more warmth across the west and up into Canada, while a trough aligns over the Midwest. By Friday, highs will be knocked back about 15° from Thursday's high, making it only to 50° Friday afternoon. But the coldest air will arrive overnight, as lows Saturday morning look to bottom out in the upper 20's in many locations. While it will be a brush of cold air, the core of the cold air will be retained north of the northern Great Lakes region.
And as quickly as the cold air arrived, it will depart through the weekend with more warmth returning into Sunday and next week. The trough lifts north again, and upper jet winds will bring mild temperatures through the middle of next week.
If temperatures do fall into the upper 20's Friday night into Saturday morning it would be the first freeze for the Rockford region of the season, which would be a new record. Our typical first freeze arrives in the beginning of October, and the latest fall freeze Rockford recorded previously was November 4th, 1973.