Calcutta climate

Calcutta Frost Dates and Growing Season

NOAA 1991-2020 normals for Montgomery L&d, 16.3 km from Calcutta, elevation 690 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Montgomery L&d. 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 28 and the first fall freeze around October 26, a growing season of about 178 days.

Median at 36°F
last May 9, first October 13
Median at 32°F
last April 28, first October 26
Median at 28°F
last April 17, first November 4

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 24May 20May 16May 12May 9May 6May 2Apr 28Apr 24
32°FMay 15May 9May 5May 1Apr 28Apr 25Apr 22Apr 19Apr 15
28°FMay 4Apr 28Apr 23Apr 20Apr 17Apr 14Apr 11Apr 7Apr 2
24°FApr 18Apr 14Apr 9Apr 5Apr 3Mar 31Mar 29Mar 24Mar 19
20°FApr 4Mar 31Mar 28Mar 25Mar 22Mar 19Mar 15Mar 10Mar 5
16°FMar 26Mar 21Mar 17Mar 14Mar 11Mar 8Mar 4Mar 1Feb 23

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

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°F175169164159155152147142134
32°F197191186182178174169163156
28°F223216210207202198193188179
24°F248240235230226221217211204
20°F278268261256251246240234226
16°F301292286280276271265259249

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
5,811
Cooling degree days, base 65°F
635
Growing degree days, base 40°F
5,155
Growing degree days, base 45°F
3,967
Growing degree days, base 50°F
2,917
Growing degree days, base 55°F
2,009
Growing degree days, base 60°F
1,243

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,14702
February97702
March828022
April4623107
May20033311
June39121533
July6217676
August9182639
September8772436
October3698161
November698026
December99003

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 16.3 km from Calcutta. 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 USC00365902 (Montgomery L&d). Public domain.