Nasty Frost and Freeze Tonight in Vermont, Rest of Interior Northeast

Frost on a flower last autumn in St. Albans, Vermont.
Similar scenes are likely tomorrow morning.  

The growing season is about to come to an end in a wide swath of northern New York, pretty much all of Vermont, New Hampshire and Maine, and in many valleys of the Northeast.

Freeze and frost warnings are up for this entire region as temperatures tonight will go down into the 20s  and low 30s.

The Adirondacks and the northern half of Vermont outside the Champlain Valley are under a freeze warning, as temperatures there are expected to fall below 32 degrees.

In the Champlain Valley and southern Vermont, there's a frost advisory up for tonight for temperatures expected to be between 32 and 35 degrees.

Here's why there's a frost advisory in those places: Temperatures are normally measured at five feet off the ground. On clear, calm nights, the temperature might go down to 33 or 34 degrees, so you think, "Phew! no frost."

But you'd be wrong. Right down at ground level, five feet below the thermometer, it's often one to three degrees colder than what the thermometer is reading. . So you can get a damaging frost even though the temperature officially never sank below 32 degrees.

In the "warmer" areas under a frost advisory, you probably can save most of your flowers and garden veggies by covering them up.  And of course you can bring potted plants indoors.

But for valleys in the Adirondacks of New York,  and much of Vermont and New Hampshire, I wonder if even covering plants will be enough as temperatures slump into the 20s.

Whether this upcoming frost and freeze is earlier than normal depends upon where exactly you are. For many people, this frost and freeze will come one to three weeks earlier than normal. But for other areas, it's right on schedule.

In Vermont, the first frost of the fall season normally hits anywhere between early September in the cold hollows of the Northeast Kingdom to mid-October near Lake Champlain. (Early September frosts are also pretty normal in Adirondack valleys like around Saranac Lake and in parts of northern New Hampshire)

Those cold spots have already had frosts and freezes this month, so they already had their normal end to the growing season.

In central and eastern Vermont, tonight's expected freeze is about one to two weeks earlier than normal, says the National Weather Service in South Burlington.

In Vermont, the water in Lake Champlain maintains its warmth into the fall, and that helps keep that area a little warmer, and usually delays the first freeze of the season.

The first 32 degree reading of the season in Burlington, Vermont is around October 7. I'm not sure if Burlington will reach 32 degrees tonight, but it will be close.

If it does, it won't be the earliest 32 degree reading on record. The earliest 32 on record was on Sept. 13, 1964.  The record low for Friday morning in Burlington is 32 degrees, set in 1955, so we might flirt with tying or breaking the record low for the date.

Because the Champlain Islands between New York and Vermont are surrounded by warm-ish lake water, that area is the only one in the interior Northeast not under any kind of frost or freeze advisory. It should stay at least a few degrees above freezing in places like South Hero, Vermont and Cumberland Head, New York.

The northern half of New Hampshire and much of Maine is under a freeze watch for tonight, and I bet that will be upgraded to a warning later today.

After a brief warm up this weekend, it will turn chilly again for a few days early next week. The National Weather Service in Burlington, Vermont said there's even the possibility of the first snow flurries of the season atop higher mountains like Jay Peak and Mount Mansfield Monday night or Tuesday morning.