Mason climate

Mason Frost Dates and Growing Season

NOAA 1991-2020 normals for Mason, 0.1 km from Mason, elevation 1531 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mason. 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 March 18 and the first fall freeze around November 13, a growing season of about 241 days.

Median at 36°F
last April 3, first November 4
Median at 32°F
last March 18, first November 13
Median at 28°F
last March 4, first November 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.

Threshold10%20%30%40%50%60%70%80%90%
36°FApr 20Apr 15Apr 11Apr 6Apr 3Mar 31Mar 26Mar 19Mar 12
32°FApr 7Apr 1Mar 27Mar 21Mar 18Mar 14Mar 9Mar 4Feb 28
28°FMar 22Mar 16Mar 12Mar 8Mar 4Mar 1Feb 25Feb 19Feb 9
24°FMar 12Mar 7Mar 2Feb 25Feb 18Feb 11Feb 3Jan 27Jan 13
20°FMar 4Feb 20Feb 9Feb 1Jan 27Jan 21Jan 14Jan 4Dec 20
16°FFeb 15Feb 4Jan 30Jan 24Jan 18Jan 14Jan 7Jan 1Dec 22

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°FOct 20Oct 25Oct 29Nov 1Nov 4Nov 6Nov 10Nov 14Nov 20
32°FOct 30Nov 2Nov 6Nov 10Nov 13Nov 17Nov 22Nov 26Dec 1
28°FNov 7Nov 13Nov 18Nov 22Nov 26Nov 30Dec 3Dec 8Dec 17
24°FNov 19Nov 26Dec 1Dec 5Dec 10Dec 17Dec 24Dec 30Jan 8
20°FNov 30Dec 9Dec 15Dec 25Dec 31Jan 3Jan 10Jan 18Feb 1
16°FDec 12Dec 27Jan 1Jan 4Jan 8Jan 14Jan 19Jan 30Feb 7

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°F240230224218214209205200193
32°F268257251246241237231225216
28°F296286278273268262257250241
24°F336325315305299291285275265
20°F365365355346337329320306295
16°F365365365365365365357345331

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
99% of years
20°F or colder
79% of years
16°F or colder
35% 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
2,115
Cooling degree days, base 65°F
2,517
Growing degree days, base 40°F
9,611
Growing degree days, base 45°F
7,915
Growing degree days, base 50°F
6,330
Growing degree days, base 55°F
4,894
Growing degree days, base 60°F
3,614

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January549277
February3877128
March24330285
April84102472
May12279732
June0458907
July05631,028
August05611,026
September4356802
October76134529
November27223244
December4893102

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

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00415650 (Mason). Public domain.