Diamond City climate

Diamond City Frost Dates and Growing Season

NOAA 1991-2020 normals for Lead Hill, 5.1 km from Diamond City, elevation 830 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lead Hill. 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 15 and the first fall freeze around October 22, a growing season of about 189 days.

Median at 36°F
last April 27, first October 12
Median at 32°F
last April 15, first October 22
Median at 28°F
last April 4, first November 1

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 11May 6May 2Apr 30Apr 27Apr 25Apr 22Apr 17Apr 13
32°FMay 1Apr 26Apr 23Apr 19Apr 15Apr 13Apr 9Apr 5Mar 30
28°FApr 20Apr 14Apr 11Apr 7Apr 4Apr 1Mar 29Mar 24Mar 17
24°FApr 8Apr 3Mar 31Mar 27Mar 23Mar 19Mar 14Mar 10Mar 4
20°FMar 29Mar 23Mar 18Mar 13Mar 9Mar 5Mar 2Feb 27Feb 22
16°FMar 19Mar 11Mar 6Mar 2Feb 28Feb 24Feb 19Feb 13Feb 5

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 30Oct 4Oct 7Oct 10Oct 12Oct 16Oct 18Oct 21Oct 25
32°FOct 7Oct 13Oct 17Oct 20Oct 22Oct 25Oct 27Oct 31Nov 4
28°FOct 18Oct 23Oct 26Oct 30Nov 1Nov 3Nov 6Nov 10Nov 15
24°FOct 28Nov 1Nov 4Nov 7Nov 10Nov 14Nov 18Nov 23Nov 30
20°FNov 4Nov 9Nov 14Nov 18Nov 23Nov 27Dec 1Dec 4Dec 11
16°FNov 13Nov 21Nov 27Dec 1Dec 5Dec 10Dec 15Dec 21Dec 30

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°F186180176172168165161157150
32°F207201197193189184179174167
28°F233225219214210207202196188
24°F258249243237233228224218210
20°F281271267260255250245240231
16°F309298292286280275269261251

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
4,493
Cooling degree days, base 65°F
1,268
Growing degree days, base 40°F
6,593
Growing degree days, base 45°F
5,232
Growing degree days, base 50°F
4,019
Growing degree days, base 55°F
2,955
Growing degree days, base 60°F
2,037

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January97009
February770018
March584377
April30014210
May10582445
June8251693
July1383848
August2349812
September46157562
October26528264
November569269
December874014

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 5.1 km from Diamond City. 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 USC00034106 (Lead Hill). Public domain.