Hemlock climate

Hemlock Frost Dates and Growing Season

NOAA 1991-2020 normals for Hemlock, 2.2 km from Hemlock, elevation 902 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hemlock. 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 2 and the first fall freeze around October 18, a growing season of about 167 days.

Median at 36°F
last May 12, first October 5
Median at 32°F
last May 2, first October 18
Median at 28°F
last April 22, first November 1

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 26May 22May 18May 15May 12May 10May 7May 3Apr 29
32°FMay 16May 12May 8May 5May 2Apr 30Apr 28Apr 25Apr 22
28°FMay 6May 1Apr 28Apr 25Apr 22Apr 20Apr 17Apr 13Apr 7
24°FApr 23Apr 19Apr 16Apr 13Apr 10Apr 7Apr 4Apr 2Mar 30
20°FApr 13Apr 8Apr 5Apr 3Apr 1Mar 31Mar 29Mar 24Mar 19
16°FApr 5Apr 1Mar 31Mar 28Mar 25Mar 21Mar 18Mar 15Mar 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°FSep 23Sep 28Oct 1Oct 3Oct 5Oct 8Oct 11Oct 15Oct 20
32°FOct 2Oct 7Oct 11Oct 14Oct 18Oct 21Oct 25Oct 30Nov 3
28°FOct 14Oct 21Oct 25Oct 29Nov 1Nov 3Nov 5Nov 9Nov 14
24°FOct 29Nov 2Nov 5Nov 8Nov 11Nov 14Nov 18Nov 22Nov 29
20°FNov 8Nov 13Nov 17Nov 20Nov 23Nov 26Dec 1Dec 3Dec 10
16°FNov 18Nov 23Nov 27Dec 1Dec 2Dec 6Dec 12Dec 17Dec 23

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°F165159154149145141137133127
32°F187181176172167163158152146
28°F210204198194190186181177170
24°F235228223220215212209204197
20°F257249243240236231228223217
16°F276269263259255251245240233

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
6,617
Cooling degree days, base 65°F
514
Growing degree days, base 40°F
4,651
Growing degree days, base 45°F
3,541
Growing degree days, base 50°F
2,574
Growing degree days, base 55°F
1,744
Growing degree days, base 60°F
1,047

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,25201
February1,09601
March97609
April580263
May26130259
June6399486
July12181634
August20143587
September12855380
October4305127
November738024
December1,06003

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 2.2 km from Hemlock. 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 USC00303773 (Hemlock). Public domain.