Elgin climate

Elgin Frost Dates and Growing Season

NOAA 1991-2020 normals for Heart Butte Dam, 21.1 km from Elgin, elevation 2134 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Heart Butte 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 May 14 and the first fall freeze around September 29, a growing season of about 136 days.

Median at 36°F
last May 24, first September 20
Median at 32°F
last May 14, first September 29
Median at 28°F
last May 5, first October 6

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 5Jun 1May 29May 26May 24May 21May 19May 16May 13
32°FMay 28May 23May 20May 17May 14May 12May 9May 7May 3
28°FMay 18May 14May 10May 7May 5May 3May 1Apr 28Apr 21
24°FMay 9May 4May 1Apr 29Apr 26Apr 22Apr 18Apr 15Apr 11
20°FApr 30Apr 25Apr 21Apr 17Apr 14Apr 12Apr 9Apr 6Apr 3
16°FApr 19Apr 14Apr 11Apr 9Apr 7Apr 4Apr 2Mar 30Mar 23

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 4Sep 10Sep 14Sep 17Sep 20Sep 22Sep 25Sep 27Oct 1
32°FSep 16Sep 20Sep 24Sep 26Sep 29Oct 1Oct 4Oct 7Oct 10
28°FSep 23Sep 28Oct 1Oct 4Oct 6Oct 8Oct 11Oct 14Oct 18
24°FOct 1Oct 5Oct 8Oct 11Oct 14Oct 17Oct 19Oct 23Oct 27
20°FOct 7Oct 13Oct 16Oct 20Oct 23Oct 25Oct 28Nov 1Nov 6
16°FOct 16Oct 22Oct 26Oct 29Oct 31Nov 3Nov 6Nov 10Nov 15

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°F13512912512111711411010598
32°F153147142139136132128124118
28°F173166161157153150146140134
24°F191185180176172168164159152
20°F209203198194191187182176169
16°F227219213209206202198193187

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
8,599
Cooling degree days, base 65°F
477
Growing degree days, base 40°F
4,001
Growing degree days, base 45°F
3,047
Growing degree days, base 50°F
2,214
Growing degree days, base 55°F
1,506
Growing degree days, base 60°F
921

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,58900
February1,32600
March1,11304
April700133
May35913184
June9971424
July24191632
August43162585
September22239291
October648259
November1,05303
December1,42600

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 21.1 km from Elgin. 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 USC00324091 (Heart Butte Dam). Public domain.