Bystrom climate

Bystrom Frost Dates and Growing Season

NOAA 1991-2020 normals for Modesto City CO AP, 3.1 km from Bystrom, elevation 73 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Modesto City CO 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 January 31 and the first fall freeze around December 5, a growing season of about 312 days.

Median at 36°F
last March 1, first November 22
Median at 32°F
last January 31, first December 5
Median at 28°F
last January 8, first December 21

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°FMar 31Mar 18Mar 11Mar 5Mar 1Feb 26Feb 22Feb 15Feb 3
32°FFeb 25Feb 18Feb 10Feb 5Jan 31Jan 25Jan 18Jan 10Dec 31
28°FFeb 6Jan 29Jan 21Jan 14Jan 8Jan 3Dec 31Dec 25Dec 16
24°FJan 22Jan 15Jan 10Jan 4Jan 1Dec 31Dec 27Dec 20Dec 13
20°F–––––––––
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°FNov 8Nov 12Nov 16Nov 20Nov 22Nov 25Nov 28Dec 1Dec 9
32°FNov 20Nov 25Nov 29Dec 2Dec 5Dec 10Dec 16Dec 23Jan 6
28°FDec 1Dec 5Dec 11Dec 16Dec 21Dec 28Jan 1Jan 8Jan 20
24°FDec 5Dec 13Dec 18Dec 23Dec 27Dec 31Jan 1Jan 9Jan 15
20°F–––––––––
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°F294283275268262256249242231
32°F343333324318312306298291279
28°F365365365360352345340333321
24°F365365365365365365365364351
20°F365365365365365365365365365
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
97% of years
28°F or colder
68% of years
24°F or colder
20% of years
20°F or colder
3% of years
16°F or colder
0% 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
2,300
Cooling degree days, base 65°F
1,624
Growing degree days, base 40°F
8,457
Growing degree days, base 45°F
6,690
Growing degree days, base 50°F
5,078
Growing degree days, base 55°F
3,700
Growing degree days, base 60°F
2,553

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January544028
February364088
March2623214
April14629334
May44133553
June5288734
July0429894
August0395860
September4269716
October6875473
November3182154
December546030

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 3.1 km from Bystrom. 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 USW00023258 (Modesto City CO AP). Public domain.