Normandy Park climate

Normandy Park Frost Dates and Growing Season

NOAA 1991-2020 normals for Seattle Tacoma Intl AP, 2.2 km from Normandy Park, elevation 370 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Seattle Tacoma Intl 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 2 and the first fall freeze around November 23, a growing season of about 266 days.

Median at 36°F
last March 31, first November 7
Median at 32°F
last March 2, first November 23
Median at 28°F
last February 4, first December 10

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 21Apr 12Apr 6Apr 2Mar 31Mar 28Mar 24Mar 18Mar 13
32°FMar 23Mar 16Mar 12Mar 7Mar 2Feb 27Feb 22Feb 16Feb 5
28°FFeb 28Feb 23Feb 18Feb 13Feb 4Jan 27Jan 17Jan 5Dec 20
24°FFeb 17Feb 4Jan 25Jan 15Jan 4Dec 30Dec 19Dec 13Dec 5
20°FJan 28Jan 14Jan 1Dec 27Dec 18Dec 14Dec 11Dec 6Nov 30
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 24Oct 29Nov 1Nov 4Nov 7Nov 11Nov 14Nov 17Nov 23
32°FNov 6Nov 11Nov 14Nov 18Nov 23Nov 28Dec 2Dec 7Dec 15
28°FNov 17Nov 24Nov 30Dec 5Dec 10Dec 15Dec 23Jan 1Jan 16
24°FNov 26Dec 3Dec 8Dec 12Dec 17Dec 24Jan 1Jan 10Feb 1
20°FNov 26Dec 4Dec 8Dec 12Dec 16Dec 21Dec 29Jan 2Jan 24
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°F244235229224219215210204195
32°F298286279272266260254246239
28°F352339331322315307300289277
24°F365365365365355344336329316
20°F365365365365365365365363339
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
95% of years
24°F or colder
64% of years
20°F or colder
25% of years
16°F or colder
4% 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
4,376
Cooling degree days, base 65°F
265
Growing degree days, base 40°F
5,128
Growing degree days, base 45°F
3,572
Growing degree days, base 50°F
2,324
Growing degree days, base 55°F
1,389
Growing degree days, base 60°F
700

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January68706
February58807
March557025
April412177
May2429236
June11829362
July3196530
August2498539
September10230378
October3491137
November555023
December71105

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 2.2 km from Normandy Park. 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 USW00024233 (Seattle Tacoma Intl AP). Public domain.