Highland Holiday climate

Highland Holiday Frost Dates and Growing Season

NOAA 1991-2020 normals for Hillsboro, 12.7 km from Highland Holiday, elevation 953 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hillsboro. 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 24 and the first fall freeze around October 20, a growing season of about 178 days.

Median at 36°F
last May 4, first October 10
Median at 32°F
last April 24, first October 20
Median at 28°F
last April 12, 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 20May 14May 10May 7May 4Apr 30Apr 28Apr 26Apr 21
32°FMay 11May 5Apr 30Apr 27Apr 24Apr 21Apr 18Apr 15Apr 10
28°FApr 29Apr 22Apr 18Apr 16Apr 12Apr 9Apr 6Apr 3Mar 31
24°FApr 17Apr 12Apr 8Apr 5Apr 2Mar 31Mar 29Mar 23Mar 18
20°FApr 6Apr 2Mar 31Mar 28Mar 24Mar 20Mar 17Mar 12Mar 5
16°FMar 31Mar 24Mar 20Mar 17Mar 14Mar 9Mar 5Mar 1Feb 22

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 27Oct 1Oct 4Oct 6Oct 10Oct 12Oct 14Oct 16Oct 20
32°FOct 6Oct 12Oct 15Oct 18Oct 20Oct 22Oct 25Oct 27Nov 1
28°FOct 17Oct 22Oct 25Oct 29Nov 1Nov 2Nov 5Nov 8Nov 13
24°FOct 31Nov 2Nov 4Nov 7Nov 10Nov 13Nov 17Nov 21Nov 28
20°FNov 6Nov 10Nov 13Nov 17Nov 20Nov 25Nov 29Dec 3Dec 10
16°FNov 13Nov 18Nov 23Nov 27Dec 1Dec 5Dec 10Dec 17Dec 25

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°F175170165161157153149145137
32°F196190186182178174169164157
28°F221213208205201196192187180
24°F245236231225221218214210203
20°F270261254248244239233228220
16°F293284276271265260255247239

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
5,441
Cooling degree days, base 65°F
829
Growing degree days, base 40°F
5,631
Growing degree days, base 45°F
4,386
Growing degree days, base 50°F
3,283
Growing degree days, base 55°F
2,317
Growing degree days, base 60°F
1,499

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,11305
February92408
March747146
April4009150
May16463373
June24174600
July2256719
August7217676
September8094466
October34814189
November669043
December96609

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 12.7 km from Highland Holiday. 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 USC00333758 (Hillsboro). Public domain.