Ames Lake climate

Ames Lake Frost Dates and Growing Season

NOAA 1991-2020 normals for Snoqualmie Falls, 14.1 km from Ames Lake, elevation 440 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Snoqualmie Falls. 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 30 and the first fall freeze around November 7, a growing season of about 223 days.

Median at 36°F
last April 26, first October 22
Median at 32°F
last March 30, first November 7
Median at 28°F
last February 27, first November 29

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 13May 7May 2Apr 29Apr 26Apr 22Apr 18Apr 14Apr 8
32°FApr 21Apr 13Apr 8Apr 3Mar 30Mar 25Mar 20Mar 13Mar 4
28°FMar 25Mar 17Mar 9Mar 2Feb 27Feb 22Feb 15Feb 6Jan 16
24°FFeb 28Feb 24Feb 17Feb 9Jan 31Jan 18Jan 4Dec 22Dec 6
20°FFeb 25Feb 18Feb 6Jan 26Jan 8Dec 31Dec 19Dec 8Dec 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 4Oct 10Oct 14Oct 18Oct 22Oct 25Oct 29Nov 1Nov 7
32°FOct 22Oct 28Nov 1Nov 3Nov 7Nov 11Nov 17Nov 24Dec 1
28°FNov 6Nov 12Nov 19Nov 25Nov 29Dec 4Dec 11Dec 19Dec 31
24°FNov 21Nov 28Dec 5Dec 11Dec 18Dec 27Jan 3Jan 14Feb 6
20°FNov 28Dec 4Dec 9Dec 17Dec 28Jan 4Jan 14Feb 3Feb 21
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°F206197190184180175170164156
32°F252242234228223217210204195
28°F319306295285277268259250236
24°F365359346337328318310302284
20°F365365365365365362345332315
16°F365365365365365365365365363

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
99% of years
24°F or colder
83% of years
20°F or colder
42% of years
16°F or colder
10% 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
4,991
Cooling degree days, base 65°F
151
Growing degree days, base 40°F
4,472
Growing degree days, base 45°F
3,019
Growing degree days, base 50°F
1,889
Growing degree days, base 55°F
1,058
Growing degree days, base 60°F
481

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January74104
February63106
March606019
April465056
May3114172
June17317295
July6158462
August5460471
September16911294
October419094
November609015
December75202

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 14.1 km from Ames Lake. 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 USC00457773 (Snoqualmie Falls). Public domain.