Downieville climate

Downieville Frost Dates and Growing Season

NOAA 1991-2020 normals for Downieville, 0.5 km from Downieville, elevation 2915 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Downieville. 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 28 and the first fall freeze around October 25, a growing season of about 178 days.

Median at 36°F
last May 24, first October 8
Median at 32°F
last April 28, first October 25
Median at 28°F
last April 6, first November 10

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 11Jun 5Jun 1May 28May 24May 19May 14May 9May 2
32°FMay 22May 12May 6May 1Apr 28Apr 25Apr 22Apr 18Apr 13
28°FApr 25Apr 19Apr 15Apr 10Apr 6Apr 1Mar 27Mar 19Mar 10
24°FMar 30Mar 9Mar 2Feb 26Feb 20Feb 13Feb 4Jan 23Jan 8
20°FFeb 19Feb 8Jan 27Jan 18Jan 8Jan 2Dec 29Dec 21Dec 11
16°FJan 27Jan 18Jan 8Jan 1Dec 29Dec 23Dec 19Dec 14Dec 6

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 24Sep 28Oct 2Oct 5Oct 8Oct 11Oct 14Oct 18Oct 22
32°FOct 9Oct 15Oct 19Oct 22Oct 25Oct 28Oct 31Nov 3Nov 8
28°FOct 28Nov 1Nov 4Nov 7Nov 10Nov 14Nov 19Nov 25Dec 1
24°FNov 10Nov 16Nov 22Nov 28Dec 1Dec 5Dec 10Dec 17Dec 26
20°FNov 27Dec 3Dec 9Dec 15Dec 20Dec 26Jan 1Jan 8Jan 24
16°FDec 3Dec 10Dec 16Dec 19Dec 24Dec 30Jan 3Jan 12Jan 25

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°F161154148142137132126119110
32°F201193188183178173168161150
28°F254241233225219214208201192
24°F330315303295288277267257244
20°F365365362354347339332322307
16°F365365365365365365365360346

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
78% of years
16°F or colder
26% 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
4,757
Cooling degree days, base 65°F
455
Growing degree days, base 40°F
5,106
Growing degree days, base 45°F
3,753
Growing degree days, base 50°F
2,642
Growing degree days, base 55°F
1,731
Growing degree days, base 60°F
1,006

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January80600
February65804
March611027
April465076
May26313238
June9459418
July10172628
August11143597
September7362441
October3026195
November620018
December84600

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 0.5 km from Downieville. 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 USC00042500 (Downieville). Public domain.