Pasadena climate

Pasadena Frost Dates and Growing Season

NOAA 1991-2020 normals for Baltimore Wash Intl AP, 11 km from Pasadena, elevation 156 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Baltimore Wash Intl AP. 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 April 10 and the first fall freeze around October 31, a growing season of about 204 days.

Median at 36°F
last April 24, first October 21
Median at 32°F
last April 10, first October 31
Median at 28°F
last March 28, first November 10

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 12May 6May 1Apr 28Apr 24Apr 21Apr 18Apr 15Apr 9
32°FApr 25Apr 19Apr 16Apr 13Apr 10Apr 7Apr 3Mar 31Mar 27
28°FApr 10Apr 5Apr 2Mar 31Mar 28Mar 24Mar 21Mar 18Mar 13
24°FMar 31Mar 26Mar 22Mar 19Mar 16Mar 12Mar 9Mar 4Feb 28
20°FMar 20Mar 15Mar 11Mar 7Mar 4Mar 1Feb 25Feb 21Feb 13
16°FMar 10Mar 4Feb 28Feb 25Feb 20Feb 15Feb 9Feb 3Jan 28

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

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°F200193188184179176172165158
32°F223216212208204200196192183
28°F249242236232228224220215208
24°F280271264259254250245239231
20°F307299293288282277270264255
16°F334325319314308303298292283

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
99% 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
4,484
Cooling degree days, base 65°F
1,322
Growing degree days, base 40°F
6,560
Growing degree days, base 45°F
5,203
Growing degree days, base 50°F
4,007
Growing degree days, base 55°F
2,962
Growing degree days, base 60°F
2,068

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January95107
February794010
March642252
April31819194
May10990447
June11266705
July0411876
August1346811
September36163578
October26024250
November544163
December820015

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 11 km from Pasadena. 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 USW00093721 (Baltimore Wash Intl AP). Public domain.