Perth climate

Perth Frost Dates and Growing Season

NOAA 1991-2020 normals for Gloversville 7NW (peck Lake), 21.5 km from Perth, elevation 1455 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Gloversville 7NW (peck Lake). 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 11 and the first fall freeze around October 3, a growing season of about 143 days.

Median at 36°F
last May 23, first September 23
Median at 32°F
last May 11, first October 3
Median at 28°F
last May 1, first October 14

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 3May 31May 28May 25May 23May 20May 17May 14May 10
32°FMay 25May 21May 17May 14May 11May 9May 7May 3Apr 30
28°FMay 13May 9May 6May 3May 1Apr 29Apr 26Apr 23Apr 19
24°FMay 2Apr 28Apr 24Apr 22Apr 20Apr 17Apr 15Apr 11Apr 8
20°FApr 21Apr 17Apr 14Apr 11Apr 9Apr 7Apr 5Apr 3Mar 31
16°FApr 13Apr 9Apr 6Apr 4Apr 2Apr 1Mar 30Mar 26Mar 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 10Sep 15Sep 17Sep 20Sep 23Sep 25Sep 27Sep 30Oct 3
32°FSep 20Sep 24Sep 28Oct 1Oct 3Oct 5Oct 7Oct 10Oct 15
28°FOct 1Oct 5Oct 8Oct 11Oct 14Oct 16Oct 19Oct 23Oct 28
24°FOct 13Oct 18Oct 21Oct 24Oct 27Oct 31Nov 1Nov 5Nov 9
20°FOct 26Oct 30Nov 1Nov 4Nov 7Nov 9Nov 12Nov 15Nov 18
16°FNov 4Nov 9Nov 12Nov 15Nov 17Nov 19Nov 22Nov 26Dec 1

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°F139133129125122119115111105
32°F160155150146143139136131125
28°F184178173169165161158153147
24°F206201196192188185181176170
20°F226221217213210207204199194
16°F246239235231228225221217211

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
8,675
Cooling degree days, base 65°F
163
Growing degree days, base 40°F
3,383
Growing degree days, base 45°F
2,477
Growing degree days, base 50°F
1,692
Growing degree days, base 55°F
1,026
Growing degree days, base 60°F
499

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,52500
February1,33100
March1,21401
April788012
May3935147
June13132354
July3877503
August8437419
September26513219
October642035
November96601
December1,30000

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 21.5 km from Perth. 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 USC00303322 (Gloversville 7NW (peck Lake)). Public domain.