Trail climate

Trail Frost Dates and Growing Season

NOAA 1991-2020 normals for Lost Creek Dam, 11.4 km from Trail, elevation 1580 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lost Creek Dam. 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 29 and the first fall freeze around October 17, a growing season of about 171 days.

Median at 36°F
last May 18, first October 2
Median at 32°F
last April 29, first October 17
Median at 28°F
last March 31, 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°FJun 7May 31May 26May 21May 18May 14May 11May 6May 1
32°FMay 19May 11May 5May 1Apr 29Apr 25Apr 21Apr 15Apr 7
28°FApr 28Apr 19Apr 11Apr 5Mar 31Mar 26Mar 19Mar 12Mar 3
24°FMar 25Mar 14Mar 7Mar 1Feb 25Feb 19Feb 10Jan 31Jan 16
20°FFeb 24Feb 15Feb 4Jan 26Jan 15Jan 6Dec 31Dec 21Dec 9
16°FJan 24Jan 14Jan 6Jan 1Dec 28Dec 24Dec 16Dec 10Dec 2

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 17Sep 22Sep 26Sep 29Oct 2Oct 4Oct 7Oct 11Oct 15
32°FOct 1Oct 6Oct 10Oct 13Oct 17Oct 20Oct 23Oct 28Nov 1
28°FOct 16Oct 21Oct 24Oct 28Nov 1Nov 4Nov 10Nov 18Dec 1
24°FNov 1Nov 6Nov 12Nov 21Nov 27Dec 2Dec 9Dec 17Dec 27
20°FNov 9Nov 26Dec 2Dec 8Dec 13Dec 21Dec 28Jan 4Jan 20
16°FNov 29Dec 4Dec 9Dec 14Dec 20Dec 25Dec 30Jan 4Jan 16

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°F158149144140135130125119109
32°F197188182177171166161154146
28°F251240231223216209203193183
24°F315302290280272264254245233
20°F365361349340333324314305290
16°F365365365365365365357347336

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
99% of years
20°F or colder
82% of years
16°F or colder
37% 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
4,683
Cooling degree days, base 65°F
564
Growing degree days, base 40°F
5,219
Growing degree days, base 45°F
3,821
Growing degree days, base 50°F
2,697
Growing degree days, base 55°F
1,799
Growing degree days, base 60°F
1,095

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January78001
February62905
March584029
April438291
May25117246
June10957399
July15206656
August15196646
September8681447
October3456161
November622015
December80902

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 11.4 km from Trail. 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 USC00355055 (Lost Creek Dam). Public domain.