Parker Strip Frost Dates and Growing Season

NOAA 1991-2020 normals for Parker Resrvoir, 8.3 km from Parker Strip, elevation 738 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Parker Resrvoir. 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 7 and the first fall freeze around December 31, a growing season of about 365 days.

Median at 36°F: last January 23, first December 20
Median at 32°F: last January 7, first December 31

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 25	Feb 15	Feb 6	Jan 31	Jan 23	Jan 16	Jan 9	Jan 3	Dec 27
32°F	Feb 6	Jan 28	Jan 18	Jan 12	Jan 7	Jan 2	Dec 30	Dec 25	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	Nov 30	Dec 7	Dec 11	Dec 15	Dec 20	Dec 23	Dec 27	Dec 31	Jan 11
32°F	Dec 10	Dec 18	Dec 23	Dec 27	Dec 31	Jan 2	Jan 9	Jan 15	Jan 28
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	361	352	344	338	331	325	316	305	291
32°F	365	365	365	365	365	364	358	348	336
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: 95% of years
32°F or colder: 51% of years
28°F or colder: 7% of years
24°F or colder: 1% 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: 1,129
Cooling degree days, base 65°F: 4,511
Growing degree days, base 40°F: 12,508
Growing degree days, base 45°F: 10,690
Growing degree days, base 50°F: 8,907
Growing degree days, base 55°F: 7,246
Growing degree days, base 60°F: 5,779

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	331	0	152
February	200	10	236
March	88	86	464
April	21	227	656
May	3	488	950
June	0	756	1,206
July	0	933	1,398
August	0	914	1,379
September	0	690	1,140
October	9	341	797
November	118	65	399
December	360	1	130

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 8.3 km from Parker Strip. 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 USC00046699 (Parker Resrvoir). Public domain.