Murphys climate

Murphys Frost Dates and Growing Season

NOAA 1991-2020 normals for New Melones Dam Hq, 15 km from Murphys, elevation 960 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for New Melones Dam Hq. 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 February 20 and the first fall freeze around December 11, a growing season of about 290 days.

Median at 36°F
last April 7, first November 24
Median at 32°F
last February 20, first December 11
Median at 28°F
last January 6, first December 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 5Apr 22Apr 16Apr 11Apr 7Apr 1Mar 24Mar 12Mar 1
32°FApr 7Mar 22Mar 7Feb 28Feb 20Feb 14Feb 6Jan 25Jan 10
28°FFeb 15Feb 5Jan 26Jan 13Jan 6Dec 31Dec 29Dec 23Dec 16
24°FJan 15Dec 31Dec 30Dec 28Dec 25Dec 21Dec 18Dec 16Dec 12
20°F–––––––––
16°F–––––––––

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°FNov 3Nov 12Nov 17Nov 21Nov 24Nov 28Dec 2Dec 6Dec 12
32°FNov 24Nov 30Dec 4Dec 7Dec 11Dec 15Dec 20Dec 28Jan 8
28°FDec 5Dec 12Dec 17Dec 20Dec 24Dec 28Jan 2Jan 11Feb 1
24°FDec 10Dec 15Dec 18Dec 20Dec 25Dec 27Dec 29Dec 31Jan 5
20°F–––––––––
16°F–––––––––

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°F270255244236229223215207194
32°F335319309300290282272258238
28°F365365365365358352344335320
24°F365365365365365365365365364
20°F365365365365365365365365365
16°F365365365365365365365365365

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
99% of years
28°F or colder
60% of years
24°F or colder
12% of years
20°F or colder
1% of years
16°F or colder
0% 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
2,547
Cooling degree days, base 65°F
1,842
Growing degree days, base 40°F
8,430
Growing degree days, base 45°F
6,679
Growing degree days, base 50°F
5,108
Growing degree days, base 55°F
3,791
Growing degree days, base 60°F
2,721

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January535032
February416063
March3382159
April23119251
May87115494
June15292728
July0504969
August0476941
September8321763
October74107498
November3056177
December539033

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 15 km from Murphys. 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 USC00046174 (New Melones Dam Hq). Public domain.