Silver Summit climate

Silver Summit Frost Dates and Growing Season

NOAA 1991-2020 normals for Wanship Dam, 8.7 km from Silver Summit, elevation 5940 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Wanship 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 June 11 and the first fall freeze around September 12, a growing season of about 92 days.

Median at 32°F
last June 11, first September 12
Median at 28°F
last May 26, first September 23

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°F–––––––––
32°FJun 30Jun 24Jun 20Jun 15Jun 11Jun 7Jun 2May 29May 21
28°FJun 15Jun 8Jun 3May 30May 26May 20May 16May 11May 5
24°FMay 29May 20May 15May 10May 6May 2Apr 28Apr 23Apr 16
20°FMay 9May 1Apr 26Apr 21Apr 17Apr 13Apr 8Apr 4Mar 28
16°FApr 20Apr 12Apr 7Apr 4Apr 1Mar 28Mar 24Mar 18Mar 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°F–––––––––
32°FAug 28Sep 2Sep 6Sep 9Sep 12Sep 15Sep 19Sep 22Sep 27
28°FSep 5Sep 12Sep 16Sep 20Sep 23Sep 25Sep 29Oct 2Oct 7
24°FSep 16Sep 23Sep 28Oct 1Oct 3Oct 6Oct 11Oct 16Oct 22
20°FOct 1Oct 5Oct 11Oct 15Oct 19Oct 22Oct 26Oct 31Nov 4
16°FOct 13Oct 19Oct 23Oct 27Oct 30Nov 2Nov 5Nov 9Nov 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°F888276716762564940
32°F115108102969286817464
28°F14313512912311811410810191
24°F176167161155151145139133124
20°F209201194189184179173166157
16°F235227220215211206201195185

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
7,437
Cooling degree days, base 65°F
260
Growing degree days, base 40°F
3,717
Growing degree days, base 45°F
2,711
Growing degree days, base 50°F
1,868
Growing degree days, base 55°F
1,178
Growing degree days, base 60°F
638

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,26500
February1,04000
March87903
April645023
May4122124
June16427321
July26128567
August3889516
September22114260
October583052
November92103
December1,24300

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 8.7 km from Silver Summit. 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 USC00429165 (Wanship Dam). Public domain.