White River Junction climate

White River Junction Frost Dates and Growing Season

NOAA 1991-2020 normals for Lebanon Muni AP, 2.8 km from White River Junction, elevation 598 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lebanon Muni AP. 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 9 and the first fall freeze around October 6, a growing season of about 148 days.

Median at 36°F
last May 22, first September 26
Median at 32°F
last May 9, first October 6
Median at 28°F
last April 29, first October 15

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°FJun 6Jun 2May 29May 26May 22May 20May 16May 12May 7
32°FMay 24May 20May 16May 12May 9May 6May 4May 1Apr 27
28°FMay 11May 7May 3Apr 30Apr 29Apr 26Apr 24Apr 21Apr 17
24°FApr 30Apr 25Apr 22Apr 20Apr 17Apr 14Apr 11Apr 8Apr 4
20°FApr 18Apr 14Apr 10Apr 8Apr 5Apr 3Apr 2Mar 30Mar 23
16°FApr 8Apr 4Apr 2Mar 31Mar 29Mar 26Mar 22Mar 18Mar 14

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 12Sep 17Sep 20Sep 23Sep 26Sep 28Oct 1Oct 3Oct 7
32°FSep 23Sep 28Oct 1Oct 3Oct 6Oct 8Oct 11Oct 14Oct 19
28°FOct 3Oct 7Oct 10Oct 13Oct 15Oct 18Oct 22Oct 26Nov 1
24°FOct 13Oct 18Oct 21Oct 25Oct 28Oct 31Nov 3Nov 5Nov 11
20°FOct 26Oct 31Nov 2Nov 5Nov 8Nov 11Nov 15Nov 18Nov 23
16°FNov 7Nov 11Nov 15Nov 18Nov 21Nov 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°F144138133129125121117112106
32°F167160155152148144141136128
28°F190182177174170167163158152
24°F212206202197193190185181174
20°F234228223219216213208203197
16°F257250245241237233228223216

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
7,333
Cooling degree days, base 65°F
461
Growing degree days, base 40°F
4,294
Growing degree days, base 45°F
3,263
Growing degree days, base 50°F
2,364
Growing degree days, base 55°F
1,584
Growing degree days, base 60°F
944

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,40100
February1,19100
March1,02805
April624245
May27720232
June7580455
July14176628
August27140578
September16941329
October511284
November83309
December1,18401

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 2.8 km from White River Junction. 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 USW00094765 (Lebanon Muni AP). Public domain.