Royal Oak climate

Royal Oak Frost Dates and Growing Season

NOAA 1991-2020 normals for Farmington, 18 km from Royal Oak, elevation 720 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Farmington. 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 1 and the first fall freeze around October 17, a growing season of about 165 days.

Median at 36°F
last May 13, first October 4
Median at 32°F
last May 1, first October 17
Median at 28°F
last April 22, first October 27

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 27May 23May 19May 16May 13May 9May 6May 3Apr 30
32°FMay 16May 11May 8May 4May 1Apr 29Apr 27Apr 23Apr 19
28°FMay 5Apr 30Apr 27Apr 24Apr 22Apr 19Apr 16Apr 13Apr 8
24°FApr 23Apr 19Apr 16Apr 13Apr 9Apr 6Apr 4Apr 2Mar 28
20°FApr 14Apr 7Apr 4Apr 2Mar 31Mar 28Mar 23Mar 19Mar 14
16°FApr 3Mar 31Mar 27Mar 23Mar 20Mar 17Mar 14Mar 10Mar 3

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

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°F162156152148144141137132125
32°F183177172169165161157152146
28°F206199195191187183179175168
24°F229223219215211208204200195
20°F255247241237233228224220214
16°F279270264259254249244239232

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
6,867
Cooling degree days, base 65°F
573
Growing degree days, base 40°F
4,603
Growing degree days, base 45°F
3,533
Growing degree days, base 50°F
2,601
Growing degree days, base 55°F
1,794
Growing degree days, base 60°F
1,109

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,30200
February1,12800
March968113
April588054
May26825250
June50116516
July10207662
August17166614
September13654372
October4665110
November804011
December1,12801

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 km from Royal Oak. 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 USC00202691 (Farmington). Public domain.