Salem climate

Salem Frost Dates and Growing Season

NOAA 1991-2020 normals for Salem, 1.3 km from Salem, elevation 1205 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Salem. 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 17 and the first fall freeze around October 18, a growing season of about 182 days.

Median at 36°F
last April 30, first October 8
Median at 32°F
last April 17, first October 18
Median at 28°F
last April 3, first October 30

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 16May 11May 7May 3Apr 30Apr 27Apr 23Apr 19Apr 14
32°FMay 5Apr 29Apr 24Apr 20Apr 17Apr 13Apr 9Apr 5Mar 31
28°FApr 20Apr 14Apr 9Apr 6Apr 3Mar 31Mar 28Mar 23Mar 16
24°FApr 8Apr 2Mar 30Mar 27Mar 23Mar 19Mar 16Mar 12Mar 6
20°FMar 30Mar 24Mar 20Mar 16Mar 13Mar 10Mar 6Mar 1Feb 24
16°FMar 20Mar 14Mar 10Mar 7Mar 4Feb 28Feb 25Feb 21Feb 13

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 25Sep 30Oct 3Oct 6Oct 8Oct 11Oct 13Oct 17Oct 21
32°FOct 3Oct 9Oct 12Oct 15Oct 18Oct 21Oct 24Oct 28Oct 31
28°FOct 15Oct 20Oct 23Oct 27Oct 30Nov 1Nov 4Nov 7Nov 14
24°FOct 25Oct 31Nov 3Nov 5Nov 8Nov 12Nov 16Nov 21Nov 27
20°FNov 3Nov 6Nov 11Nov 15Nov 19Nov 23Nov 28Dec 1Dec 7
16°FNov 11Nov 17Nov 22Nov 27Dec 1Dec 4Dec 8Dec 13Dec 21

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°F181173168163160155151147138
32°F204198192186182178173168160
28°F229221216212208204198192183
24°F253244238233229223219214206
20°F276267260255249244239233226
16°F297287280275269264258252244

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
4,671
Cooling degree days, base 65°F
1,168
Growing degree days, base 40°F
6,445
Growing degree days, base 45°F
5,108
Growing degree days, base 50°F
3,910
Growing degree days, base 55°F
2,850
Growing degree days, base 60°F
1,934

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,01707
February791018
March601484
April29023234
May10988448
June14225661
July1350814
August3316778
September60135527
October27825256
November596271
December911012

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 1.3 km from Salem. 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 USC00237506 (Salem). Public domain.