For the first time this autumn we're forecasting a low of 32º at Bradley Airport this Saturday morning. Lucky us. Some areas of the state have already been below freezing and Saturday looks like it will be the coldest morning yet.
That got me to thinking - how early should we expect the first freeze of the fall across the state? The average date of the first 32º temeprature ranges from October 2nd in the Bakersville section of New Hartford to November 3rd in Bridgeport at Sikorsky Airport.
As you can see on this map areas in inland Connecticut - particularly in outlying regions typically see a freeze by the first or second week in fall while places closer to the shoreline see a typical first freeze closer to the start of November.
The setup for Friday night is a classic one for a freeze. High pressure overhead should result in cloudless skies and calm winds. This allows for what we call radiational cooling to take place - where radiation from earth readily escapes into space and the lowest few meters of the atmosphere can get very cold. It's not unusual to see a temperature of 32º at the official measuring height of 2 meters and a temperature 5 or more degrees cooler an inch off the ground.
Radiational cooling favors valley locations rather than the hills - and that's why the valley in Bakersville sees an average first freeze on October 2nd while the much higher Great Mountain Forest observing site in Norfolk has an average first freeze of October 8th.
Bring in your tender vegetation if you want it to last for a few more days!