Trego climate

Trego Frost Dates and Growing Season

NOAA 1991-2020 normals for Fortine 1 N, 8.5 km from Trego, elevation 3000 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Fortine 1 N. 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 16 and the first fall freeze around September 18, a growing season of about 121 days.

Median at 36°F
last June 2, first September 4
Median at 32°F
last May 16, first September 18
Median at 28°F
last May 1, first October 2

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 23Jun 15Jun 10Jun 6Jun 2May 31May 28May 23May 18
32°FJun 3May 28May 23May 20May 16May 13May 9May 7May 3
28°FMay 20May 13May 8May 4May 1Apr 28Apr 25Apr 20Apr 14
24°FMay 4Apr 26Apr 21Apr 16Apr 12Apr 8Apr 4Apr 1Mar 24
20°FApr 14Apr 6Apr 1Mar 30Mar 25Mar 21Mar 16Mar 11Mar 5
16°FMar 28Mar 22Mar 17Mar 13Mar 9Mar 5Mar 2Feb 26Feb 18

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°FAug 20Aug 25Aug 30Sep 2Sep 4Sep 7Sep 10Sep 14Sep 22
32°FSep 1Sep 6Sep 10Sep 14Sep 18Sep 21Sep 26Sep 30Oct 5
28°FSep 15Sep 22Sep 26Sep 30Oct 2Oct 5Oct 10Oct 14Oct 19
24°FSep 30Oct 4Oct 9Oct 14Oct 19Oct 23Oct 26Oct 31Nov 5
20°FOct 8Oct 17Oct 22Oct 27Oct 31Nov 3Nov 8Nov 14Nov 21
16°FOct 22Oct 30Nov 2Nov 7Nov 11Nov 16Nov 21Nov 27Dec 4

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°F114106100959086817464
32°F14413713112712111611110597
28°F178170163159154148144138129
24°F213203197191186181176169159
20°F247238231225220214208201191
16°F275265258251246241234227219

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
7,857
Cooling degree days, base 65°F
209
Growing degree days, base 40°F
3,405
Growing degree days, base 45°F
2,434
Growing degree days, base 50°F
1,635
Growing degree days, base 55°F
991
Growing degree days, base 60°F
514

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,27700
February1,05400
March91801
April650014
May3823137
June19813268
July52108521
August7177472
September2838200
October676023
November99601
December1,30000

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 8.5 km from Trego. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00243139 (Fortine 1 N). Public domain.