Needles Frost Dates and Growing Season

NOAA 1991-2020 normals for Needles AP, 9 km from Needles, elevation 890 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Needles AP. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

A freeze (32°F or colder) happens in only 37 percent of years at Needles AP, so there is no typical freeze season.

Median at 36°F: last January 15, first December 21
Median at 32°F: last January 6, first January 2

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Feb 20	Feb 7	Jan 30	Jan 22	Jan 15	Jan 10	Jan 3	Dec 29	Dec 18
32°F	Feb 10	Jan 29	Jan 16	Jan 11	Jan 6	Jan 3	Dec 31	Dec 25	Dec 16
28°F	–	–	–	–	–	–	–	–	–
24°F	–	–	–	–	–	–	–	–	–
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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Nov 30	Dec 6	Dec 12	Dec 16	Dec 21	Dec 26	Dec 30	Jan 3	Jan 18
32°F	Dec 11	Dec 21	Dec 27	Dec 30	Jan 2	Jan 6	Jan 12	Jan 21	Feb 5
28°F	–	–	–	–	–	–	–	–	–
24°F	–	–	–	–	–	–	–	–	–
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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	365	359	352	345	339	331	323	313	302
32°F	365	365	365	365	365	365	362	354	340
28°F	365	365	365	365	365	365	365	365	365
24°F	365	365	365	365	365	365	365	365	365
20°F	365	365	365	365	365	365	365	365	365
16°F	365	365	365	365	365	365	365	365	365

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder: 88% of years
32°F or colder: 37% of years
28°F or colder: 4% of years
24°F or colder: 0% of years
20°F or colder: 0% 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: 941
Cooling degree days, base 65°F: 5,049
Growing degree days, base 40°F: 13,233
Growing degree days, base 45°F: 11,411
Growing degree days, base 50°F: 9,615
Growing degree days, base 55°F: 7,913
Growing degree days, base 60°F: 6,382

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	275	2	204
February	161	18	280
March	62	112	515
April	12	273	711
May	1	562	1,026
June	0	840	1,290
July	0	1,040	1,505
August	0	1,003	1,468
September	0	749	1,199
October	5	379	839
November	105	70	416
December	319	2	164

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

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USW00023179 (Needles AP). Public domain.