Murphy climate

Murphy Frost Dates and Growing Season

NOAA 1991-2020 normals for Swan Falls Ph, 14.4 km from Murphy, elevation 2325 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Swan Falls Ph. 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 12 and the first fall freeze around October 26, a growing season of about 193 days.

Median at 36°F
last April 28, first October 15
Median at 32°F
last April 12, first October 26
Median at 28°F
last March 23, first November 5

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 21May 11May 5May 1Apr 28Apr 25Apr 22Apr 18Apr 11
32°FMay 6Apr 28Apr 22Apr 17Apr 12Apr 8Apr 4Mar 31Mar 23
28°FApr 25Apr 11Apr 3Mar 29Mar 23Mar 16Mar 12Mar 6Feb 28
24°FApr 2Mar 18Mar 8Mar 3Feb 28Feb 25Feb 20Feb 14Feb 7
20°FMar 2Feb 25Feb 21Feb 17Feb 12Feb 8Feb 3Jan 29Jan 16
16°FFeb 20Feb 14Feb 8Feb 4Jan 30Jan 23Jan 14Jan 5Dec 27

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 30Oct 5Oct 9Oct 12Oct 15Oct 17Oct 20Oct 24Oct 29
32°FOct 9Oct 17Oct 21Oct 24Oct 26Oct 29Oct 31Nov 4Nov 9
28°FOct 21Oct 27Oct 30Nov 1Nov 5Nov 9Nov 12Nov 16Nov 21
24°FOct 28Nov 2Nov 8Nov 12Nov 15Nov 20Nov 23Nov 27Dec 2
20°FNov 4Nov 11Nov 16Nov 23Nov 26Nov 30Dec 3Dec 9Dec 18
16°FNov 13Nov 22Nov 29Dec 2Dec 7Dec 12Dec 18Dec 26Jan 8

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°F189181175170166161156149136
32°F219211205199193187180173162
28°F254244237229224216210200187
24°F287277269264257251243232217
20°F324312303295288282277269257
16°F351338331323316308301293282

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
97% 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
4,826
Cooling degree days, base 65°F
1,283
Growing degree days, base 40°F
6,187
Growing degree days, base 45°F
4,867
Growing degree days, base 50°F
3,721
Growing degree days, base 55°F
2,756
Growing degree days, base 60°F
1,949

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January97200
February72503
March549040
April3545139
May14364390
June33200617
July2460924
August3404866
September50138539
October32312189
November702014
December97001

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 14.4 km from Murphy. 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 USC00108928 (Swan Falls Ph). Public domain.