Clear skies, light wind and a cool air mass allowed the temperature to fall below freezing Sunday morning for the first time this autumn at the Fairbanks International Airport. This is about a week later than average for the Airport (median date since the observations have been at Fairbanks IA is September 8th) Many, though not all valley location had one or more freezes in late August (most widespread on the 25th). A few hillside areas have yet to freeze; the low at Keystone Ridge Sunday morning was 33F but with frost, and the Nenana Hills RWIS reported a low of 36F (though the thermometer sensor is 4 meters or more above the ground).
The plot below shows the raw date (not adjusted for leap years) of the date of first freeze at the Fairbanks Airport. As you can see, September15th is in keeping with first freeze dates over the past 15 years.