Fall River Mills climate

Fall River Mills Frost Dates and Growing Season

NOAA 1991-2020 normals for Hat Creek, 12 km from Fall River Mills, elevation 3015 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hat Creek. 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 29 and the first fall freeze around September 19, a growing season of about 113 days.

Median at 32°F
last May 29, first September 19
Median at 28°F
last May 6, first October 4

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 23Jun 13Jun 6Jun 2May 29May 24May 18May 13May 8
28°FJun 3May 22May 15May 10May 6May 3Apr 30Apr 26Apr 19
24°FMay 12May 2Apr 27Apr 22Apr 19Apr 13Apr 8Apr 3Mar 28
20°FApr 21Apr 10Apr 3Mar 29Mar 23Mar 17Mar 11Mar 6Feb 26
16°FMar 13Mar 6Mar 2Feb 27Feb 21Feb 17Feb 11Feb 4Jan 23

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°FSep 5Sep 10Sep 14Sep 17Sep 19Sep 22Sep 25Sep 29Oct 4
28°FSep 19Sep 26Sep 29Oct 2Oct 4Oct 7Oct 11Oct 16Oct 22
24°FOct 3Oct 9Oct 13Oct 16Oct 20Oct 23Oct 27Nov 1Nov 7
20°FOct 16Oct 22Oct 27Nov 1Nov 3Nov 7Nov 11Nov 18Nov 24
16°FOct 30Nov 5Nov 10Nov 14Nov 19Nov 24Nov 28Dec 3Dec 11

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°F1019387827772665948
32°F1381301241181131081019585
28°F174166159154149144138131118
24°F212202195189184178172164153
20°F255244237231224218210203192
16°F305292284276269264257249237

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
5,608
Cooling degree days, base 65°F
340
Growing degree days, base 40°F
4,436
Growing degree days, base 45°F
3,230
Growing degree days, base 50°F
2,240
Growing degree days, base 55°F
1,438
Growing degree days, base 60°F
800

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January93200
February75500
March685010
April518057
May2919211
June11551388
July19150597
August29102538
September14027342
October439194
November73204
December95500

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 12 km from Fall River Mills. 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 USC00043824 (Hat Creek). Public domain.