Lewiston climate

Lewiston Frost Dates and Growing Season

NOAA 1991-2020 normals for Atlanta, 18.7 km from Lewiston, elevation 879 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Atlanta. 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 May 22 and the first fall freeze around September 27, a growing season of about 127 days.

Median at 36°F
last June 3, first September 14
Median at 32°F
last May 22, first September 27
Median at 28°F
last May 8, first October 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°FJun 23Jun 15Jun 10Jun 6Jun 3Jun 1May 29May 25May 21
32°FJun 5May 31May 28May 25May 22May 20May 16May 11May 5
28°FMay 24May 20May 16May 12May 8May 5May 1Apr 29Apr 24
24°FMay 13May 5May 1Apr 29Apr 26Apr 23Apr 20Apr 16Apr 12
20°FApr 28Apr 22Apr 18Apr 16Apr 13Apr 9Apr 6Apr 4Apr 1
16°FApr 17Apr 11Apr 7Apr 5Apr 3Apr 2Mar 31Mar 27Mar 21

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 1Sep 4Sep 8Sep 11Sep 14Sep 18Sep 20Sep 24Sep 29
32°FSep 12Sep 18Sep 21Sep 24Sep 27Sep 30Oct 2Oct 6Oct 11
28°FSep 26Sep 30Oct 4Oct 7Oct 11Oct 15Oct 19Oct 23Oct 29
24°FOct 9Oct 16Oct 21Oct 25Oct 29Nov 1Nov 3Nov 8Nov 14
20°FOct 26Oct 31Nov 3Nov 6Nov 10Nov 14Nov 17Nov 20Nov 26
16°FNov 6Nov 11Nov 16Nov 19Nov 22Nov 25Nov 29Dec 3Dec 9

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°F12211511010610298938877
32°F149142137132127123118113106
28°F177171165160155150145140134
24°F205199193189184180175168159
20°F230223217213209205201196190
16°F252244239235231226222217209

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
8,158
Cooling degree days, base 65°F
332
Growing degree days, base 40°F
3,736
Growing degree days, base 45°F
2,787
Growing degree days, base 50°F
1,970
Growing degree days, base 55°F
1,273
Growing degree days, base 60°F
718

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,45400
February1,28000
March1,14906
April729029
May38115169
June12366397
July49129545
August6490491
September23828259
October581368
November89306
December1,21800

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 18.7 km from Lewiston. 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 USC00200342 (Atlanta). Public domain.