Parker Frost Dates and Growing Season

NOAA 1991-2020 normals for Parker, 0.5 km from Parker, elevation 420 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Parker. 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 January 12 and the first fall freeze around December 19, a growing season of about 338 days.

Median at 36°F: last February 7, first December 6
Median at 32°F: last January 12, first December 19
Median at 28°F: last January 1, first December 26

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	Mar 3	Feb 25	Feb 19	Feb 14	Feb 7	Feb 1	Jan 27	Jan 19	Jan 9
32°F	Feb 15	Feb 4	Jan 27	Jan 20	Jan 12	Jan 7	Jan 3	Dec 28	Dec 20
28°F	Feb 2	Jan 15	Jan 10	Jan 5	Jan 1	Dec 30	Dec 25	Dec 20	Dec 14
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 24	Nov 28	Dec 1	Dec 4	Dec 6	Dec 9	Dec 12	Dec 16	Dec 22
32°F	Dec 4	Dec 8	Dec 11	Dec 15	Dec 19	Dec 23	Dec 27	Jan 1	Jan 10
28°F	Dec 10	Dec 14	Dec 19	Dec 23	Dec 26	Dec 30	Jan 3	Jan 9	Jan 21
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	331	323	315	308	302	296	290	282	274
32°F	365	357	350	344	338	334	325	316	304
28°F	365	365	365	365	365	364	357	349	339
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: 100% of years
32°F or colder: 88% of years
28°F or colder: 42% of years
24°F or colder: 7% 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: 1,049
Cooling degree days, base 65°F: 4,416
Growing degree days, base 40°F: 12,492
Growing degree days, base 45°F: 10,671
Growing degree days, base 50°F: 8,880
Growing degree days, base 55°F: 7,198
Growing degree days, base 60°F: 5,704

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	308	1	170
February	181	9	252
March	74	71	462
April	15	209	644
May	1	465	929
June	0	735	1,185
July	0	916	1,381
August	0	911	1,376
September	0	704	1,154
October	6	335	794
November	108	60	403
December	355	1	132

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 0.5 km from Parker. 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 USC00026250 (Parker). Public domain.