Sevenmile climate

Sevenmile Frost Dates and Growing Season

NOAA 1991-2020 normals for Mc Nary 2N, 37.7 km from Sevenmile, elevation 7340 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mc Nary 2N. 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 20 and the first fall freeze around October 11, a growing season of about 142 days.

Median at 36°F
last June 1, first October 2
Median at 32°F
last May 20, first October 11
Median at 28°F
last May 6, first October 22

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 8Jun 5Jun 3Jun 1May 30May 26May 22May 19
32°FJun 4May 31May 26May 23May 20May 17May 14May 9May 5
28°FMay 23May 16May 13May 9May 6May 3May 1Apr 28Apr 22
24°FMay 10May 4Apr 30Apr 26Apr 23Apr 19Apr 15Apr 11Apr 5
20°FApr 26Apr 17Apr 12Apr 8Apr 4Mar 31Mar 26Mar 17Mar 10
16°FApr 6Mar 30Mar 20Mar 13Mar 9Mar 5Feb 28Feb 21Feb 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°FSep 21Sep 25Sep 28Oct 1Oct 2Oct 5Oct 7Oct 11Oct 14
32°FSep 29Oct 2Oct 5Oct 8Oct 11Oct 14Oct 17Oct 20Oct 24
28°FOct 7Oct 13Oct 16Oct 19Oct 22Oct 24Oct 28Nov 1Nov 6
24°FOct 17Oct 21Oct 26Oct 30Nov 2Nov 5Nov 9Nov 15Nov 20
20°FOct 25Nov 1Nov 6Nov 10Nov 14Nov 17Nov 21Nov 24Nov 29
16°FNov 4Nov 10Nov 16Nov 19Nov 23Nov 26Nov 30Dec 5Dec 11

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°F140134130126123120117112105
32°F162155150146142138134129122
28°F189181175170167162158153147
24°F217208202197192188183177168
20°F254243235228222215210204196
16°F289278270263256250242233222

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
6,113
Cooling degree days, base 65°F
138
Growing degree days, base 40°F
4,020
Growing degree days, base 45°F
2,859
Growing degree days, base 50°F
1,900
Growing degree days, base 55°F
1,123
Growing degree days, base 60°F
519

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,00300
February84100
March77204
April606022
May3653152
June9137398
July3263496
August5531442
September1705288
October456088
November723011
December1,00000

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 37.7 km from Sevenmile. 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 USC00025412 (Mc Nary 2N). Public domain.