Havre North climate

Havre North Frost Dates and Growing Season

NOAA 1991-2020 normals for Havre City CO AP, 7.2 km from Havre North, elevation 2585 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Havre City CO 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 May 15 and the first fall freeze around September 23, a growing season of about 129 days.

Median at 36°F
last May 27, first September 12
Median at 32°F
last May 15, first September 23
Median at 28°F
last May 3, first October 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 11Jun 5Jun 2May 30May 27May 25May 23May 20May 16
32°FMay 27May 24May 20May 17May 15May 13May 11May 8May 3
28°FMay 16May 11May 8May 6May 3May 1Apr 29Apr 25Apr 20
24°FMay 4May 1Apr 28Apr 25Apr 22Apr 19Apr 16Apr 11Apr 7
20°FApr 29Apr 22Apr 19Apr 15Apr 12Apr 8Apr 4Mar 31Mar 24
16°FApr 18Apr 11Apr 8Apr 5Apr 2Mar 30Mar 25Mar 19Mar 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°FAug 29Sep 3Sep 6Sep 10Sep 12Sep 16Sep 18Sep 20Sep 23
32°FSep 11Sep 16Sep 19Sep 21Sep 23Sep 26Sep 28Oct 1Oct 5
28°FSep 19Sep 23Sep 26Sep 29Oct 1Oct 3Oct 6Oct 9Oct 15
24°FSep 26Oct 1Oct 4Oct 7Oct 11Oct 14Oct 17Oct 20Oct 26
20°FOct 3Oct 9Oct 14Oct 17Oct 20Oct 24Oct 27Oct 30Nov 4
16°FOct 13Oct 18Oct 23Oct 26Oct 29Nov 1Nov 4Nov 7Nov 14

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°F123117112108105101979184
32°F146140136132129126122118112
28°F168161157153150146143139133
24°F192184179175170166163158150
20°F213206200195191186181176168
16°F233225219213209205200195187

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
8,174
Cooling degree days, base 65°F
406
Growing degree days, base 40°F
3,929
Growing degree days, base 45°F
2,930
Growing degree days, base 50°F
2,077
Growing degree days, base 55°F
1,369
Growing degree days, base 60°F
808

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,46500
February1,22401
March1,02204
April632033
May3548169
June13043366
July26176615
August49154572
September24123259
October649154
November1,02305
December1,36100

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 7.2 km from Havre North. 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 USW00094012 (Havre City CO AP). Public domain.