Oracle climate

Oracle Frost Dates and Growing Season

NOAA 1991-2020 normals for Oracle 2 Se, 3.6 km from Oracle, elevation 4510 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Oracle 2 Se. 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 23 and the first fall freeze around November 22, a growing season of about 242 days.

Median at 36°F
last April 12, first November 11
Median at 32°F
last March 23, first November 22
Median at 28°F
last February 21, first December 2

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

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°F237228222217212208202197189
32°F277266257249242236229222213
28°F320308297290283274266256242
24°F362351342333325317308297280
20°F365365365365365359351337323
16°F365365365365365365365365356

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
92% of years
20°F or colder
50% of years
16°F or colder
15% 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
2,811
Cooling degree days, base 65°F
1,845
Growing degree days, base 40°F
8,222
Growing degree days, base 45°F
6,565
Growing degree days, base 50°F
5,091
Growing degree days, base 55°F
3,826
Growing degree days, base 60°F
2,753

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January609024
February489041
March3801142
April21515265
May42165588
June1414862
July0468933
August0415880
September2287735
October9278454
November3683144
December614023

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 3.6 km from Oracle. 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 USC00026119 (Oracle 2 Se). Public domain.