Fall is showing more and more of its presence across the Twin Tiers. More trees are starting to show their colors and the nights have become a bit chilly.
A Canadian high will build in over the weekend, bringing very dry air and very chilly conditions at night. It appears we have all the ingredients for very good radiational cooling Saturday night. This will be the coldest night of the next 5 days, and the coldest since June 1st, when we hit 37 degrees at the airport. We are now watching for the possibility for frost Sunday morning. At this juncture it appears that the sheltered/rural valley locations have the best chance for frost, while the urban areas should remain frost free. The normally cold spots could see temperatures drop into the 34-37 degree range. Brrrr!
How normal is frost in September? Well the average first frost occurs between September 30th - October 10th for most areas along and west of I-81. East of I-81 the average first frost occurs between September 20th - September 30th. Only the highest elevations of Delaware County see it earlier than the 20th. At this time of year it is difficult to get freezing temperatures. However, temperatures below freezing have occurred as early as September 20th, 1993 at the Binghamton Regional Airport when the temperature dropped to 29 degrees.