Zimmerman climate

Zimmerman Frost Dates and Growing Season

NOAA 1991-2020 normals for Elk Rvr, 15.4 km from Zimmerman, elevation 880 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Elk Rvr. 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 4 and the first fall freeze around October 5, a growing season of about 154 days.

Median at 36°F
last May 13, first September 28
Median at 32°F
last May 4, first October 5
Median at 28°F
last April 25, first October 17

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°FMay 28May 24May 20May 16May 13May 11May 7May 4May 1
32°FMay 18May 13May 10May 7May 4May 2Apr 30Apr 26Apr 22
28°FMay 9May 4May 1Apr 29Apr 25Apr 22Apr 19Apr 15Apr 11
24°FApr 29Apr 24Apr 20Apr 16Apr 14Apr 11Apr 9Apr 6Apr 2
20°FApr 18Apr 13Apr 10Apr 8Apr 6Apr 3Apr 1Mar 29Mar 23
16°FApr 11Apr 6Apr 4Apr 1Mar 31Mar 27Mar 24Mar 20Mar 15

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 16Sep 20Sep 23Sep 26Sep 28Sep 30Oct 2Oct 5Oct 9
32°FSep 23Sep 28Oct 1Oct 3Oct 5Oct 8Oct 11Oct 14Oct 18
28°FOct 3Oct 7Oct 11Oct 14Oct 17Oct 19Oct 22Oct 25Oct 29
24°FOct 14Oct 19Oct 22Oct 25Oct 27Oct 30Nov 1Nov 5Nov 9
20°FOct 25Oct 30Nov 1Nov 4Nov 6Nov 9Nov 12Nov 16Nov 21
16°FNov 1Nov 6Nov 8Nov 11Nov 14Nov 17Nov 20Nov 23Nov 29

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°F152146142138134131127122115
32°F171165161157154150146141135
28°F193187182178174171167161155
24°F215209204199195192188183176
20°F235227223218215211207203196
16°F251244239235230226222216210

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
569
Growing degree days, base 40°F
4,398
Growing degree days, base 45°F
3,400
Growing degree days, base 50°F
2,508
Growing degree days, base 55°F
1,739
Growing degree days, base 60°F
1,090

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,61200
February1,33000
March1,10409
April629152
May28024241
June47119522
July6228686
August21150593
September17346331
October563372
November98403
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 15.4 km from Zimmerman. 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 USC00212500 (Elk Rvr). Public domain.