Hayward climate

Hayward Frost Dates and Growing Season

NOAA 1991-2020 normals for Hayward RS, 2.2 km from Hayward, elevation 1200 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hayward RS. 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 22 and the first fall freeze around September 23, a growing season of about 124 days.

Median at 36°F
last June 4, first September 12
Median at 32°F
last May 22, first September 23
Median at 28°F
last May 8, first October 3

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 24Jun 16Jun 12Jun 7Jun 4Jun 1May 28May 24May 17
32°FJun 6Jun 1May 29May 26May 22May 19May 15May 8May 2
28°FMay 27May 21May 17May 13May 8May 4May 1Apr 29Apr 23
24°FMay 15May 9May 4Apr 30Apr 28Apr 26Apr 22Apr 19Apr 14
20°FMay 3Apr 29Apr 25Apr 22Apr 19Apr 15Apr 12Apr 8Apr 3
16°FApr 24Apr 19Apr 15Apr 12Apr 9Apr 6Apr 3Mar 31Mar 27

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°FAug 26Sep 1Sep 4Sep 8Sep 12Sep 17Sep 20Sep 25Oct 1
32°FSep 3Sep 10Sep 16Sep 19Sep 23Sep 27Oct 1Oct 4Oct 9
28°FSep 15Sep 21Sep 25Sep 29Oct 3Oct 6Oct 10Oct 14Oct 21
24°FSep 24Oct 1Oct 5Oct 10Oct 14Oct 19Oct 22Oct 28Nov 2
20°FOct 7Oct 14Oct 21Oct 25Oct 29Nov 1Nov 3Nov 7Nov 12
16°FOct 24Oct 31Nov 2Nov 5Nov 8Nov 10Nov 13Nov 18Nov 23

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°F1241161091039893888170
32°F14913913412912411911310698
28°F170162156151146141135129121
24°F192184178172168163157150141
20°F213206200195190185180174165
16°F232225220217213207202196188

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
8,344
Cooling degree days, base 65°F
406
Growing degree days, base 40°F
4,020
Growing degree days, base 45°F
3,046
Growing degree days, base 50°F
2,191
Growing degree days, base 55°F
1,456
Growing degree days, base 60°F
851

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,59800
February1,32200
March1,08508
April663247
May31523219
June8982444
July34147578
August56103512
September21546304
October585475
November97806
December1,40400

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 2.2 km from Hayward. 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 USC00473511 (Hayward RS). Public domain.