Hillview climate

Hillview Frost Dates and Growing Season

NOAA 1991-2020 normals for Louisville WFO, 6.1 km from Hillview, elevation 632 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Louisville WFO. 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 6 and the first fall freeze around November 1, a growing season of about 209 days.

Median at 36°F
last April 19, first October 23
Median at 32°F
last April 6, first November 1
Median at 28°F
last March 26, first November 11

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 5Apr 29Apr 26Apr 22Apr 19Apr 16Apr 13Apr 9Apr 4
32°FApr 23Apr 17Apr 13Apr 9Apr 6Apr 3Mar 31Mar 28Mar 23
28°FApr 9Apr 4Mar 31Mar 29Mar 26Mar 23Mar 19Mar 15Mar 9
24°FMar 29Mar 24Mar 21Mar 18Mar 15Mar 10Mar 5Mar 1Feb 22
20°FMar 20Mar 15Mar 10Mar 5Mar 2Feb 27Feb 21Feb 15Feb 7
16°FMar 11Mar 3Feb 28Feb 23Feb 16Feb 11Feb 7Feb 2Jan 25

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°FOct 11Oct 15Oct 18Oct 21Oct 23Oct 26Oct 28Oct 30Nov 4
32°FOct 21Oct 25Oct 29Oct 31Nov 1Nov 3Nov 6Nov 10Nov 15
28°FNov 1Nov 3Nov 6Nov 9Nov 11Nov 14Nov 18Nov 23Nov 29
24°FNov 7Nov 11Nov 15Nov 19Nov 23Nov 27Dec 1Dec 5Dec 13
20°FNov 16Nov 22Nov 27Dec 1Dec 4Dec 8Dec 13Dec 19Dec 26
16°FNov 28Dec 2Dec 8Dec 13Dec 19Dec 23Dec 27Jan 1Jan 9

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°F206199194190186182178172165
32°F229221217213209204200195187
28°F256247241236231227223218212
24°F280271264259254249244239231
20°F305297290284279273267261252
16°F330321314308303298292285276

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
4,279
Cooling degree days, base 65°F
1,427
Growing degree days, base 40°F
6,923
Growing degree days, base 45°F
5,536
Growing degree days, base 50°F
4,292
Growing degree days, base 55°F
3,195
Growing degree days, base 60°F
2,237

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January955014
February755022
March574586
April26831254
May82126511
June5284729
July0389854
August1366831
September33183600
October23339293
November542276
December833022

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 6.1 km from Hillview. 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 USC00154958 (Louisville WFO). Public domain.