Downs climate

Downs Frost Dates and Growing Season

NOAA 1991-2020 normals for Glen Elder Lake, 19.5 km from Downs, elevation 1500 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Glen Elder Lake. 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 April 29 and the first fall freeze around October 15, a growing season of about 168 days.

Median at 36°F
last May 7, first October 5
Median at 32°F
last April 29, first October 15
Median at 28°F
last April 17, first October 24

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 20May 16May 12May 9May 7May 4May 2Apr 29Apr 24
32°FMay 13May 8May 4May 2Apr 29Apr 26Apr 22Apr 17Apr 13
28°FMay 4Apr 30Apr 26Apr 21Apr 17Apr 15Apr 12Apr 8Apr 3
24°FApr 24Apr 17Apr 13Apr 10Apr 7Apr 4Apr 1Mar 30Mar 22
20°FApr 14Apr 8Apr 5Apr 2Mar 31Mar 26Mar 22Mar 16Mar 11
16°FApr 7Apr 2Mar 29Mar 24Mar 19Mar 14Mar 10Mar 6Mar 1

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 22Sep 26Sep 29Oct 1Oct 5Oct 8Oct 11Oct 14Oct 18
32°FSep 28Oct 3Oct 8Oct 12Oct 15Oct 17Oct 20Oct 22Oct 26
28°FOct 8Oct 14Oct 18Oct 21Oct 24Oct 26Oct 28Oct 31Nov 4
24°FOct 19Oct 24Oct 28Oct 30Nov 1Nov 4Nov 6Nov 10Nov 14
20°FOct 28Nov 1Nov 4Nov 7Nov 9Nov 12Nov 15Nov 19Nov 26
16°FNov 2Nov 8Nov 11Nov 15Nov 18Nov 22Nov 26Nov 30Dec 6

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°F168162157153149146143138132
32°F187181176172168165160155149
28°F208201195192187183179175167
24°F228221216212208203198193187
20°F248242237231226221216211203
16°F269260254248244239234227218

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
5,673
Cooling degree days, base 65°F
1,250
Growing degree days, base 40°F
5,981
Growing degree days, base 45°F
4,772
Growing degree days, base 50°F
3,698
Growing degree days, base 55°F
2,750
Growing degree days, base 60°F
1,933

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,17900
February95705
March737038
April4116136
May17057362
June14266702
July1422886
August4340801
September72141522
October33219215
November732130
December1,06501

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 19.5 km from Downs. 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 USC00143100 (Glen Elder Lake). Public domain.