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Home Frost Dates and Growing Season

NOAA 1991-2020 normals for Tacoma Narrows AP, 14.2 km from Home, elevation 292 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Tacoma Narrows AP. 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 11 and the first fall freeze around November 21, a growing season of about 254 days.

Median at 36°F
last April 11, first November 4
Median at 32°F
last March 11, first November 21
Median at 28°F
last February 13, first December 11

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 2Apr 25Apr 20Apr 15Apr 11Apr 8Apr 4Apr 1Mar 26
32°FApr 2Mar 27Mar 21Mar 16Mar 11Mar 5Mar 1Feb 23Feb 15
28°FMar 8Feb 28Feb 23Feb 18Feb 13Feb 6Jan 29Jan 13Jan 1
24°FFeb 19Feb 10Feb 1Jan 22Jan 11Jan 2Dec 21Dec 10Dec 2
20°FFeb 10Jan 29Jan 14Jan 4Jan 1Dec 23Dec 13Dec 6Dec 1
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.

Threshold10%20%30%40%50%60%70%80%90%
36°FOct 21Oct 26Oct 29Oct 31Nov 4Nov 7Nov 10Nov 14Nov 19
32°FNov 3Nov 9Nov 13Nov 16Nov 21Nov 24Nov 28Dec 2Dec 10
28°FNov 18Nov 25Dec 1Dec 5Dec 11Dec 17Dec 26Jan 1Jan 19
24°FNov 26Dec 1Dec 6Dec 12Dec 19Dec 29Jan 5Jan 20Feb 5
20°FNov 29Dec 4Dec 8Dec 15Dec 24Jan 1Jan 4Jan 17Feb 3
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.

Threshold10%20%30%40%50%60%70%80%90%
36°F228221214209204199194188181
32°F286275267260254248241234226
28°F350335326316307300291284273
24°F365365365363354343334325313
20°F365365365365365365365365346
16°F365365365365365365365365365

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
97% of years
24°F or colder
62% of years
20°F or colder
18% of years
16°F or colder
1% 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
4,884
Cooling degree days, base 65°F
132
Growing degree days, base 40°F
4,513
Growing degree days, base 45°F
3,036
Growing degree days, base 50°F
1,896
Growing degree days, base 55°F
1,051
Growing degree days, base 60°F
455

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January73302
February63102
March595014
April467046
May2994179
June16117306
July5851457
August5048463
September14712315
October398096
November596013
December74902

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 14.2 km from Home. 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 USW00094274 (Tacoma Narrows AP). Public domain.