Hill climate

Hill Frost Dates and Growing Season

NOAA 1991-2020 normals for Franklin Falls Dam, 7.1 km from Hill, elevation 450 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Franklin Falls Dam. 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 7 and the first fall freeze around October 3, a growing season of about 148 days.

Median at 36°F
last May 20, first September 27
Median at 32°F
last May 7, first October 3
Median at 28°F
last April 27, first October 13

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°FJun 1May 28May 25May 22May 20May 18May 15May 12May 7
32°FMay 20May 16May 13May 10May 7May 5May 3May 1Apr 27
28°FMay 7May 4May 1Apr 29Apr 27Apr 24Apr 22Apr 20Apr 15
24°FApr 25Apr 22Apr 19Apr 17Apr 14Apr 11Apr 8Apr 6Apr 3
20°FApr 16Apr 12Apr 8Apr 6Apr 4Apr 3Apr 1Mar 30Mar 24
16°FApr 7Apr 4Apr 2Mar 31Mar 29Mar 25Mar 22Mar 19Mar 14

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 14Sep 19Sep 22Sep 24Sep 27Sep 28Oct 1Oct 3Oct 6
32°FSep 24Sep 28Sep 30Oct 2Oct 3Oct 5Oct 8Oct 10Oct 15
28°FOct 1Oct 5Oct 8Oct 10Oct 13Oct 15Oct 19Oct 23Oct 29
24°FOct 10Oct 14Oct 18Oct 22Oct 25Oct 29Nov 1Nov 4Nov 9
20°FOct 23Oct 28Nov 1Nov 4Nov 7Nov 10Nov 14Nov 18Nov 22
16°FNov 6Nov 11Nov 15Nov 18Nov 20Nov 23Nov 26Nov 30Dec 4

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°F143138134130128124121116111
32°F163158154151148145142138132
28°F188181176172169165162158152
24°F211205201197193190186182176
20°F235228223219216212209205198
16°F256250244241237233229225219

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
7,591
Cooling degree days, base 65°F
395
Growing degree days, base 40°F
4,077
Growing degree days, base 45°F
3,081
Growing degree days, base 50°F
2,209
Growing degree days, base 55°F
1,460
Growing degree days, base 60°F
849

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,41800
February1,21400
March1,05904
April655136
May31511197
June8863427
July12163615
August32117550
September19239306
October524170
November86706
December1,21500

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 7.1 km from Hill. 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 USC00273182 (Franklin Falls Dam). Public domain.