Bethesda climate

Bethesda Frost Dates and Growing Season

NOAA 1991-2020 normals for Barnesville, 9.9 km from Bethesda, elevation 1280 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Barnesville. 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 27 and the first fall freeze around October 22, a growing season of about 177 days.

Median at 36°F
last May 6, first October 11
Median at 32°F
last April 27, first October 22
Median at 28°F
last April 16, 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 21May 16May 12May 9May 6May 3May 1Apr 27Apr 23
32°FMay 13May 8May 3Apr 30Apr 27Apr 24Apr 22Apr 18Apr 14
28°FMay 1Apr 25Apr 22Apr 19Apr 16Apr 13Apr 9Apr 5Apr 2
24°FApr 18Apr 14Apr 10Apr 7Apr 5Apr 2Mar 31Mar 28Mar 22
20°FApr 9Apr 4Apr 1Mar 29Mar 26Mar 23Mar 20Mar 17Mar 11
16°FMar 31Mar 27Mar 23Mar 20Mar 17Mar 14Mar 10Mar 6Feb 28

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 28Oct 1Oct 5Oct 8Oct 11Oct 13Oct 16Oct 19Oct 24
32°FOct 7Oct 12Oct 16Oct 19Oct 22Oct 24Oct 27Oct 30Nov 2
28°FOct 19Oct 23Oct 28Oct 31Nov 1Nov 3Nov 6Nov 10Nov 14
24°FNov 1Nov 4Nov 6Nov 9Nov 12Nov 15Nov 19Nov 23Dec 1
20°FNov 8Nov 13Nov 16Nov 20Nov 25Nov 29Dec 2Dec 6Dec 12
16°FNov 16Nov 23Nov 28Dec 1Dec 5Dec 9Dec 14Dec 21Dec 28

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°F176170164160157153150144138
32°F197191185181177174169164157
28°F218213208204200196192186178
24°F243236231226222219214210203
20°F266259253247244240235230222
16°F292283276270265260254248241

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
5,696
Cooling degree days, base 65°F
754
Growing degree days, base 40°F
5,405
Growing degree days, base 45°F
4,196
Growing degree days, base 50°F
3,119
Growing degree days, base 55°F
2,180
Growing degree days, base 60°F
1,389

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,14505
February96205
March805133
April44210132
May19049333
June36152565
July4248710
August9201657
September8482450
October35412182
November686038
December98009

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 9.9 km from Bethesda. 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 USC00330430 (Barnesville). Public domain.