The Dalles climate

The Dalles Frost Dates and Growing Season

NOAA 1991-2020 normals for The Dalles, 2.4 km from The Dalles, elevation 150 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for The Dalles. 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 23, a growing season of about 191 days.

Median at 36°F
last April 30, first October 8
Median at 32°F
last April 14, first October 23
Median at 28°F
last March 20, 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 14May 8May 5May 2Apr 30Apr 28Apr 25Apr 22Apr 18
32°FMay 1Apr 26Apr 21Apr 18Apr 14Apr 9Apr 6Apr 1Mar 27
28°FApr 9Apr 2Mar 29Mar 25Mar 20Mar 15Mar 11Mar 7Feb 28
24°FMar 15Mar 10Mar 5Mar 2Feb 27Feb 23Feb 18Feb 12Jan 31
20°FMar 4Feb 27Feb 22Feb 16Feb 9Feb 1Jan 19Jan 8Dec 30
16°FFeb 26Feb 17Feb 8Jan 31Jan 20Jan 10Jan 2Dec 25Dec 10

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

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°F181174169165161157153148141
32°F215206201196191186180175166
28°F259249241235229224219212203
24°F306293284276269262255246237
20°F351337326317308302292282266
16°F365365357347337329318309296

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
95% of years
16°F or colder
78% 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
4,890
Cooling degree days, base 65°F
738
Growing degree days, base 40°F
5,421
Growing degree days, base 45°F
4,087
Growing degree days, base 50°F
2,973
Growing degree days, base 55°F
2,053
Growing degree days, base 60°F
1,309

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January89701
February71503
March605020
April3952101
May18736320
June6298486
July8264721
August7255713
September7980452
October3644146
November676011
December89601

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 2.4 km from The Dalles. 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 USC00358407 (The Dalles). Public domain.