Ephrata climate

Ephrata Frost Dates and Growing Season

NOAA 1991-2020 normals for Ephrata Muni AP, 3.1 km from Ephrata, elevation 1252 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ephrata 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 April 22 and the first fall freeze around October 17, a growing season of about 175 days.

Median at 36°F
last May 4, first October 5
Median at 32°F
last April 22, first October 17
Median at 28°F
last April 6, first October 27

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 22May 15May 10May 7May 4May 1Apr 29Apr 26Apr 22
32°FMay 6May 1Apr 29Apr 25Apr 22Apr 19Apr 16Apr 13Apr 8
28°FApr 25Apr 19Apr 13Apr 10Apr 6Apr 4Mar 31Mar 27Mar 19
24°FApr 7Apr 1Mar 28Mar 22Mar 15Mar 11Mar 7Mar 3Feb 26
20°FMar 19Mar 11Mar 5Mar 1Feb 27Feb 22Feb 17Feb 12Feb 4
16°FMar 4Feb 27Feb 23Feb 17Feb 12Feb 7Feb 2Jan 26Jan 12

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 22Sep 28Oct 1Oct 3Oct 5Oct 8Oct 11Oct 14Oct 17
32°FOct 3Oct 8Oct 12Oct 15Oct 17Oct 19Oct 22Oct 24Oct 28
28°FOct 14Oct 19Oct 22Oct 25Oct 27Oct 30Nov 1Nov 4Nov 10
24°FOct 24Oct 28Oct 31Nov 3Nov 6Nov 10Nov 14Nov 18Nov 23
20°FNov 1Nov 5Nov 10Nov 14Nov 17Nov 21Nov 25Nov 28Dec 6
16°FNov 9Nov 15Nov 20Nov 24Nov 27Dec 1Dec 6Dec 13Dec 24

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°F171165160156153149145139132
32°F196188184180175172167163156
28°F225216210206202198193188181
24°F259250244239233227222215206
20°F297285276270264259253246236
16°F327316306297290284277269261

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
5,753
Cooling degree days, base 65°F
843
Growing degree days, base 40°F
5,222
Growing degree days, base 45°F
4,032
Growing degree days, base 50°F
3,010
Growing degree days, base 55°F
2,142
Growing degree days, base 60°F
1,417

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,09900
February84100
March684010
April428290
May18140329
June53119516
July5324784
August8276733
September9480438
October4412105
November82204
December1,09900

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 3.1 km from Ephrata. 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 USW00024141 (Ephrata Muni AP). Public domain.