Mason County climate

Mason County Frost Dates and Growing Season

NOAA 1991-2020 normals for Southside 3 Nnw, 4.5 km from Mason County, elevation 576 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Southside 3 Nnw. 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 April 28 and the first fall freeze around October 19, a growing season of about 173 days.

Median at 36°F
last May 7, first October 8
Median at 32°F
last April 28, first October 19
Median at 28°F
last April 17, first October 28

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°FMay 24May 18May 14May 10May 7May 4Apr 30Apr 28Apr 24
32°FMay 14May 8May 5May 1Apr 28Apr 25Apr 22Apr 20Apr 15
28°FMay 3Apr 27Apr 22Apr 19Apr 17Apr 14Apr 11Apr 7Apr 3
24°FApr 18Apr 13Apr 10Apr 7Apr 4Apr 2Mar 31Mar 27Mar 21
20°FApr 6Apr 2Mar 30Mar 27Mar 24Mar 20Mar 18Mar 13Mar 6
16°FMar 28Mar 22Mar 19Mar 16Mar 13Mar 8Mar 4Feb 28Feb 19

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°FSep 28Oct 1Oct 4Oct 6Oct 8Oct 10Oct 13Oct 16Oct 20
32°FOct 6Oct 10Oct 14Oct 16Oct 19Oct 21Oct 23Oct 26Oct 29
28°FOct 16Oct 20Oct 23Oct 25Oct 28Oct 30Nov 1Nov 3Nov 8
24°FOct 24Oct 30Nov 1Nov 3Nov 6Nov 8Nov 11Nov 14Nov 19
20°FNov 3Nov 7Nov 10Nov 13Nov 15Nov 19Nov 22Nov 27Dec 2
16°FNov 11Nov 15Nov 20Nov 25Nov 28Dec 2Dec 6Dec 12Dec 21

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°F171165161158154149146141135
32°F189184180177173169165160153
28°F210203200196192188185180173
24°F233225221217214210206203196
20°F260252246242237233228224217
16°F290281274268262257251246237

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
100% of years
20°F or colder
100% of years
16°F or colder
100% 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
5,404
Cooling degree days, base 65°F
812
Growing degree days, base 40°F
5,580
Growing degree days, base 45°F
4,337
Growing degree days, base 50°F
3,244
Growing degree days, base 55°F
2,291
Growing degree days, base 60°F
1,476

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,08905
February90206
March769029
April3977149
May15655370
June24175601
July2259722
August4221682
September6786470
October36210172
November685028
December949010

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

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00468351 (Southside 3 Nnw). Public domain.