Onamia climate

Onamia Frost Dates and Growing Season

NOAA 1991-2020 normals for Isle 12N, 30.5 km from Onamia, elevation 1285 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Isle 12N. 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 10 and the first fall freeze around October 3, a growing season of about 144 days.

Median at 36°F
last May 24, first September 24
Median at 32°F
last May 10, first October 3
Median at 28°F
last April 30, first October 16

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 7Jun 2May 30May 27May 24May 21May 17May 13May 8
32°FMay 28May 22May 17May 13May 10May 7May 4May 1Apr 27
28°FMay 12May 7May 4May 1Apr 30Apr 27Apr 24Apr 20Apr 15
24°FMay 2Apr 29Apr 25Apr 22Apr 19Apr 16Apr 13Apr 9Apr 5
20°FApr 23Apr 18Apr 15Apr 12Apr 9Apr 7Apr 4Apr 2Mar 29
16°FApr 16Apr 11Apr 7Apr 5Apr 3Apr 1Mar 29Mar 24Mar 18

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 7Sep 14Sep 18Sep 21Sep 24Sep 26Sep 30Oct 2Oct 7
32°FSep 19Sep 24Sep 28Oct 1Oct 3Oct 5Oct 8Oct 12Oct 17
28°FOct 1Oct 5Oct 9Oct 12Oct 16Oct 18Oct 22Oct 25Oct 31
24°FOct 10Oct 16Oct 20Oct 23Oct 27Oct 30Nov 1Nov 5Nov 10
20°FOct 21Oct 27Oct 31Nov 2Nov 4Nov 8Nov 10Nov 14Nov 19
16°FOct 31Nov 4Nov 7Nov 10Nov 13Nov 15Nov 18Nov 21Nov 25

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°F14313513012612111711210799
32°F164158153149144140135130124
28°F187180175171166163158153147
24°F209202197193189185180176169
20°F227220215212208204200194189
16°F243237231227223219216211204

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
9,040
Cooling degree days, base 65°F
334
Growing degree days, base 40°F
3,781
Growing degree days, base 45°F
2,845
Growing degree days, base 50°F
2,024
Growing degree days, base 55°F
1,324
Growing degree days, base 60°F
751

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,73300
February1,44100
March1,18603
April729026
May35911176
June10858403
July35135566
August5397510
September22430277
October620159
November1,04404
December1,51100

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 30.5 km from Onamia. 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 USC00214103 (Isle 12N). Public domain.