Rupert climate

Rupert Frost Dates and Growing Season

NOAA 1991-2020 normals for Paul 1ENE, 7.1 km from Rupert, elevation 4150 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Paul 1ENE. 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 6 and the first fall freeze around October 6, a growing season of about 151 days.

Median at 36°F
last May 22, first September 24
Median at 32°F
last May 6, first October 6
Median at 28°F
last April 22, first October 18

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 12Jun 5May 31May 26May 22May 18May 15May 12May 7
32°FMay 22May 16May 13May 9May 6May 3Apr 30Apr 28Apr 23
28°FMay 7May 2Apr 28Apr 26Apr 22Apr 19Apr 16Apr 12Apr 7
24°FApr 26Apr 18Apr 14Apr 9Apr 5Apr 1Mar 28Mar 20Mar 13
20°FApr 8Mar 31Mar 24Mar 17Mar 12Mar 8Mar 5Mar 2Feb 22
16°FMar 20Mar 11Mar 7Mar 3Feb 28Feb 24Feb 20Feb 15Feb 7

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 7Sep 13Sep 17Sep 21Sep 24Sep 26Sep 30Oct 3Oct 8
32°FSep 22Sep 27Sep 30Oct 3Oct 6Oct 9Oct 13Oct 16Oct 19
28°FOct 3Oct 9Oct 12Oct 16Oct 18Oct 21Oct 23Oct 27Nov 1
24°FOct 16Oct 20Oct 23Oct 26Oct 29Nov 1Nov 4Nov 8Nov 13
20°FOct 22Oct 28Nov 1Nov 4Nov 8Nov 12Nov 15Nov 20Nov 25
16°FOct 30Nov 5Nov 11Nov 15Nov 19Nov 22Nov 25Nov 29Dec 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°F14413713212812311811210798
32°F171163158155151147143137129
28°F196190185181177173169163156
24°F232222214209204199194187178
20°F263254249243237231226219206
16°F289279273267261256250243233

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
6,962
Cooling degree days, base 65°F
413
Growing degree days, base 40°F
4,068
Growing degree days, base 45°F
3,019
Growing degree days, base 50°F
2,143
Growing degree days, base 55°F
1,423
Growing degree days, base 60°F
844

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,20100
February97000
March81205
April601135
May3438177
June13650370
July20186631
August34142574
September19927291
October562159
November89402
December1,19200

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 7.1 km from Rupert. 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 USC00106877 (Paul 1ENE). Public domain.