Desert Hills Frost Dates and Growing Season

NOAA 1991-2020 normals for Lake Havasu City, 5.8 km from Desert Hills, elevation 449 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lake Havasu City. 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 49 percent of years at Lake Havasu City, so there is no typical freeze season.

Median at 36°F: last January 25, first December 17
Median at 32°F: last January 5, first December 29

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 19	Feb 11	Feb 5	Feb 1	Jan 25	Jan 19	Jan 12	Jan 6	Dec 30
32°F	Feb 3	Jan 23	Jan 15	Jan 9	Jan 5	Jan 2	Dec 31	Dec 24	Dec 17
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	Dec 1	Dec 4	Dec 8	Dec 12	Dec 17	Dec 21	Dec 24	Dec 28	Jan 6
32°F	Dec 9	Dec 17	Dec 21	Dec 25	Dec 29	Jan 1	Jan 6	Jan 12	Jan 24
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	355	347	341	334	329	322	315	308	298
32°F	365	365	365	365	365	360	355	347	334
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: 96% of years
32°F or colder: 49% of years
28°F or colder: 6% 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: 1,148
Cooling degree days, base 65°F: 4,523
Growing degree days, base 40°F: 12,500
Growing degree days, base 45°F: 10,681
Growing degree days, base 50°F: 8,902
Growing degree days, base 55°F: 7,245
Growing degree days, base 60°F: 5,787

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	343	0	141
February	199	6	232
March	81	73	458
April	15	218	653
May	1	499	963
June	0	759	1,209
July	0	961	1,426
August	0	936	1,401
September	0	696	1,146
October	7	328	786
November	123	47	376
December	378	0	113

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 5.8 km from Desert Hills. 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 USC00024761 (Lake Havasu City). Public domain.