Middlesex climate

Middlesex Frost Dates and Growing Season

NOAA 1991-2020 normals for Montpelier 2, 7.5 km from Middlesex, elevation 530 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Montpelier 2. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around May 5 and the first fall freeze around October 9, a growing season of about 157 days.

Median at 36°F
last May 18, first October 1
Median at 32°F
last May 5, first October 9
Median at 28°F
last April 24, first October 21

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FMay 31May 27May 24May 21May 18May 15May 11May 8May 3
32°FMay 21May 16May 12May 8May 5May 2Apr 30Apr 27Apr 23
28°FMay 8May 4Apr 30Apr 27Apr 24Apr 22Apr 19Apr 16Apr 12
24°FApr 24Apr 20Apr 18Apr 14Apr 12Apr 10Apr 8Apr 6Apr 2
20°FApr 12Apr 9Apr 7Apr 5Apr 4Apr 2Apr 1Mar 30Mar 24
16°FApr 7Apr 4Apr 2Mar 31Mar 30Mar 28Mar 24Mar 20Mar 15

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FSep 17Sep 22Sep 25Sep 28Oct 1Oct 2Oct 4Oct 7Oct 13
32°FSep 28Oct 1Oct 4Oct 7Oct 9Oct 12Oct 15Oct 19Oct 24
28°FOct 6Oct 10Oct 14Oct 18Oct 21Oct 24Oct 29Nov 1Nov 6
24°FOct 18Oct 24Oct 28Oct 31Nov 2Nov 5Nov 8Nov 12Nov 17
20°FNov 1Nov 4Nov 7Nov 11Nov 14Nov 16Nov 19Nov 23Nov 27
16°FNov 9Nov 13Nov 18Nov 20Nov 23Nov 25Nov 28Dec 1Dec 6

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F152146142138134130126122115
32°F174168164160157152148144138
28°F198191186182178175170166160
24°F222215210206203199195189182
20°F240235230227223220216212207
16°F257250246242239236233228222

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
7,722
Cooling degree days, base 65°F
472
Growing degree days, base 40°F
4,230
Growing degree days, base 45°F
3,230
Growing degree days, base 50°F
2,349
Growing degree days, base 55°F
1,590
Growing degree days, base 60°F
955

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,47500
February1,25700
March1,11105
April675137
May30718214
June7991463
July14177628
August24139580
September16345340
October527275
November84609
December1,24500

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 7.5 km from Middlesex. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00435273 (Montpelier 2). Public domain.