Downsville climate

Downsville Frost Dates and Growing Season

NOAA 1991-2020 normals for Downsville Dam, 1.2 km from Downsville, elevation 1200 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Downsville 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 May 15 and the first fall freeze around October 3, a growing season of about 140 days.

Median at 36°F
last May 27, first September 24
Median at 32°F
last May 15, first October 3
Median at 28°F
last May 3, first October 13

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 8Jun 4Jun 1May 30May 27May 24May 21May 18May 12
32°FMay 30May 26May 22May 18May 15May 12May 9May 5Apr 30
28°FMay 19May 14May 9May 6May 3Apr 30Apr 28Apr 25Apr 22
24°FMay 8May 3Apr 29Apr 25Apr 22Apr 19Apr 16Apr 13Apr 8
20°FApr 22Apr 17Apr 13Apr 10Apr 8Apr 5Apr 3Apr 1Mar 28
16°FApr 11Apr 6Apr 3Apr 1Mar 31Mar 28Mar 25Mar 21Mar 17

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 11Sep 16Sep 19Sep 22Sep 24Sep 26Sep 29Oct 1Oct 5
32°FSep 21Sep 25Sep 28Oct 1Oct 3Oct 5Oct 8Oct 11Oct 16
28°FSep 28Oct 3Oct 7Oct 10Oct 13Oct 17Oct 19Oct 23Oct 29
24°FOct 9Oct 15Oct 19Oct 22Oct 27Oct 30Nov 1Nov 4Nov 9
20°FOct 21Oct 29Nov 1Nov 3Nov 6Nov 9Nov 12Nov 15Nov 20
16°FNov 4Nov 9Nov 12Nov 15Nov 18Nov 20Nov 23Nov 27Dec 1

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°F137130126121118114111107101
32°F159152147143140136131127119
28°F182174169165161157152147140
24°F208200195190187182176171163
20°F229223218215211208203198190
16°F251245239235232228225221215

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
7,169
Cooling degree days, base 65°F
344
Growing degree days, base 40°F
4,160
Growing degree days, base 45°F
3,117
Growing degree days, base 50°F
2,216
Growing degree days, base 55°F
1,441
Growing degree days, base 60°F
805

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,32300
February1,14200
March1,02907
April627139
May30712207
June8263434
July16132581
August34100532
September16435325
October503183
November80907
December1,13501

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 1.2 km from Downsville. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00302169 (Downsville Dam). Public domain.