Gilroy climate

Gilroy Frost Dates and Growing Season

NOAA 1991-2020 normals for Gilroy, 0.7 km from Gilroy, elevation 194 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Gilroy. 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 February 24 and the first fall freeze around November 27, a growing season of about 277 days.

Median at 36°F
last April 4, first November 10
Median at 32°F
last February 24, first November 27
Median at 28°F
last January 16, first December 12

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 1Apr 21Apr 15Apr 10Apr 4Mar 30Mar 23Mar 13Mar 4
32°FApr 4Mar 21Mar 8Mar 1Feb 24Feb 17Feb 11Feb 1Jan 23
28°FFeb 19Feb 5Jan 31Jan 23Jan 16Jan 9Jan 4Dec 30Dec 22
24°FJan 24Jan 18Jan 13Jan 8Jan 4Dec 30Dec 26Dec 19Dec 13
20°FJan 21Jan 19Jan 14Jan 11Jan 7Jan 4Dec 31Dec 28Dec 22
16°F–––––––––

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 20Oct 30Nov 3Nov 6Nov 10Nov 13Nov 17Nov 22Nov 29
32°FNov 10Nov 16Nov 20Nov 23Nov 27Dec 1Dec 4Dec 9Dec 18
28°FNov 24Dec 1Dec 5Dec 9Dec 12Dec 18Dec 24Jan 1Jan 14
24°FDec 8Dec 13Dec 17Dec 22Dec 27Dec 31Jan 5Jan 10Jan 19
20°FDec 19Dec 27Dec 31Jan 4Jan 6Jan 10Jan 14Jan 18Jan 21
16°F–––––––––

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°F255242233225218211204195174
32°F317303291283277268259247228
28°F365353346339333326319309295
24°F365365365365365360354347338
20°F365365365365365365365365361
16°F365365365365365365365365365

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
91% of years
24°F or colder
49% of years
20°F or colder
12% of years
16°F or colder
2% 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
2,424
Cooling degree days, base 65°F
694
Growing degree days, base 40°F
7,399
Growing degree days, base 45°F
5,610
Growing degree days, base 50°F
3,961
Growing degree days, base 55°F
2,573
Growing degree days, base 60°F
1,487

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January484049
February359093
March3011179
April21410250
May10447408
June3197516
July3177639
August2182645
September20131561
October9847414
November3042166
December505042

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 0.7 km from Gilroy. 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 USC00043417 (Gilroy). Public domain.