Salem climate

Salem Frost Dates and Growing Season

NOAA 1991-2020 normals for Norwich Public Utility Plt, 17.9 km from Salem, elevation 20 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Norwich Public Utility Plt. 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 April 14 and the first fall freeze around October 24, a growing season of about 192 days.

Median at 36°F
last April 30, first October 12
Median at 32°F
last April 14, first October 24
Median at 28°F
last April 1, first November 5

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 13May 8May 5May 2Apr 30Apr 27Apr 24Apr 20Apr 16
32°FApr 30Apr 24Apr 21Apr 18Apr 14Apr 11Apr 9Apr 6Apr 1
28°FApr 16Apr 9Apr 6Apr 4Apr 1Mar 31Mar 29Mar 25Mar 18
24°FApr 3Mar 31Mar 29Mar 26Mar 23Mar 19Mar 16Mar 13Mar 6
20°FMar 29Mar 24Mar 19Mar 16Mar 13Mar 10Mar 6Mar 3Feb 26
16°FMar 21Mar 15Mar 11Mar 7Mar 4Mar 1Feb 25Feb 20Feb 11

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°FOct 1Oct 3Oct 6Oct 8Oct 12Oct 15Oct 19Oct 23Oct 29
32°FOct 9Oct 13Oct 17Oct 20Oct 24Oct 27Oct 31Nov 3Nov 7
28°FOct 19Oct 26Oct 31Nov 2Nov 5Nov 7Nov 11Nov 14Nov 21
24°FNov 1Nov 8Nov 11Nov 14Nov 18Nov 22Nov 26Dec 1Dec 5
20°FNov 15Nov 21Nov 27Nov 30Dec 2Dec 6Dec 10Dec 15Dec 21
16°FNov 29Dec 3Dec 8Dec 12Dec 16Dec 21Dec 25Dec 30Jan 5

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°F187180175171166162159154147
32°F211206200196192188183178170
28°F236229224220216212209204197
24°F263256251247242237232227220
20°F288280274269265260255249242
16°F312303297292288283278272262

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
5,579
Cooling degree days, base 65°F
802
Growing degree days, base 40°F
5,337
Growing degree days, base 45°F
4,118
Growing degree days, base 50°F
3,066
Growing degree days, base 55°F
2,164
Growing degree days, base 60°F
1,409

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,10201
February93201
March819012
April477380
May20329297
June34138554
July2295758
August4242702
September8287457
October3589166
November641033
December92706

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 17.9 km from Salem. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00065910 (Norwich Public Utility Plt). Public domain.