Frost Advisory 3 am Until 8 am Sunday Morning

A large cold Canadian high is sitting over Fargo, North Dakota early tonight.  Although Saturday was officially the first day of fall, it does seem like it's a little to early to have frost and freezing temperatures across a large part of the northern plains into the upper mid west.  A FROST ADVISORY has been issued for  the following counties in south central Wisconsin and north central Illinois:  Rock, Winnebago, Boone, DeKalb, Ogle, and Lee from 3 am to 8 am Sunday morning.  A FREEZE WARNING has been issued for the following counties in southern Wisconsin and northwestern Illinois:  Green, Stephenson, Jo Daviess, and Carroll from 3 am until 8 am on Sunday morning.  Overnight temperatures are expected to drop into the low 30's with widespread frost.  The record low for September 23rd in Rockford is 29 degrees set in 1974.  That record does not appear to be in jeopardy.  The average date for the first 32 degree reading in the fall for Rockford is October 7th.  So, if the area reaches 32 degrees overnight, the growing season would come to an end about 2 weeks ahead of schedule.  Frost sensitive plants are threatened tonight, and it is advised that you either bring them indoors, or cover them to provide protection from the frost and freezing temperatures.  After a frosty start on Sunday morning, the sun will rapidly melt any frost that forms, and it should be gone by 8 am or shortly thereafter.  Sunday will be a sunny day, but it will be chilly with a northwest wind at 10 to 15 mph, and an afternoon high reaching around 59 degrees.  The average high this time of year is 73 degrees.  The sprawling Canadian high will move to Illinois by Sunday evening providing another clear and cold night.  There will be a good chance that frost will form across the Stateline again on Sunday night with a low in the middle 30's.  On Monday the high will shift off to the east allowing winds to become southerly.  A warm up will commence, and the afternoon temperature should top out near 70 degrees.  Monday night will not be a cold with a low in the upper 40's under mostly clear skies.  On Tuesday it should warm up into the middle 70's in advance of the next cold front dropping south out of Wisconsin.  The front will move across the area early on Tuesday night.  There is very little moisture available for the front to work on, so it should move through as a dry front.  The air behind the front is not as cold as the last one, so no large drops in temperature are expected on Wednesday, and high temperatures should still reach the upper 60's.