Rowley climate

Rowley Frost Dates and Growing Season

NOAA 1991-2020 normals for Groveland, 13.8 km from Rowley, elevation 30 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Groveland. 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 3 and the first fall freeze around October 8, a growing season of about 158 days.

Median at 36°F
last May 15, first September 30
Median at 32°F
last May 3, first October 8
Median at 28°F
last April 21, first October 20

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 21May 18May 15May 13May 10May 7May 3
32°FMay 17May 12May 8May 6May 3May 1Apr 29Apr 26Apr 22
28°FMay 4Apr 30Apr 26Apr 24Apr 21Apr 19Apr 15Apr 12Apr 7
24°FApr 19Apr 15Apr 11Apr 8Apr 6Apr 4Apr 2Mar 31Mar 27
20°FApr 6Apr 3Apr 1Mar 30Mar 28Mar 24Mar 20Mar 16Mar 11
16°FMar 31Mar 28Mar 23Mar 19Mar 17Mar 14Mar 11Mar 7Mar 2

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 17Sep 22Sep 25Sep 27Sep 30Oct 2Oct 4Oct 6Oct 10
32°FSep 28Oct 1Oct 4Oct 6Oct 8Oct 11Oct 13Oct 18Oct 23
28°FOct 5Oct 9Oct 13Oct 17Oct 20Oct 23Oct 27Oct 31Nov 4
24°FOct 18Oct 23Oct 27Oct 30Nov 1Nov 4Nov 7Nov 11Nov 17
20°FNov 1Nov 4Nov 8Nov 12Nov 15Nov 19Nov 22Nov 27Dec 2
16°FNov 14Nov 19Nov 24Nov 29Dec 1Dec 3Dec 7Dec 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°F152146142138135132128124119
32°F175169165161158154151147141
28°F201195190186182179174169162
24°F228221216212208204200195189
20°F255248242237233229224220213
16°F278271266261257252248243236

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
6,323
Cooling degree days, base 65°F
621
Growing degree days, base 40°F
4,774
Growing degree days, base 45°F
3,647
Growing degree days, base 50°F
2,670
Growing degree days, base 55°F
1,840
Growing degree days, base 60°F
1,157

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,20001
February1,02301
March904010
April544464
May25922242
June63111498
July6234693
August15185635
September13062385
October4354114
November719023
December1,02802

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 13.8 km from Rowley. 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 USC00193276 (Groveland). Public domain.