Last frost date in Roy, UT

Average last frost
April 22

The average last frost in Roy is April 22. By May 10 the chance of another 32°F night drops to 1 in 10. The first fall frost usually arrives about October 22, which leaves 180 frost-free days. An early freeze before October 7 happens one year in ten.

Safe after (10% risk)
May 10
Average first frost
Oct 22
Frost-free season
180 days
Hard freeze (28°F) ends
Apr 3
Next 7 nights in Roy

No frost in the next 7 nights

National Weather Service forecast, updated Oct 22, 12:57 UTC

  1. ThuOct 2248°
  2. FriOct 2341°
  3. SatOct 2440°
  4. SunOct 2539°
  5. MonOct 2639°
  6. TueOct 2739°
  7. WedOct 2841°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Apr 22First frost Oct 22180 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND180 frost-free days
Frost risk through the year at Ogden Hinkley Airport, 2.6 miles from Roy.

Planting calendar for Roy

Windows count forward or back from the average frost dates above. Click a crop for dates across Utah.

Start indoorsPlant outSow outdoorsFall plantingAverage last and first frost
Warm-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
TomatoesApr 29–May 13
PumpkinsMay 6–May 20
SunflowersApr 22–May 13
CucumbersMay 6–May 13
CornApr 29–May 13
Sweet potatoesMay 13–May 27
WatermelonMay 6–May 20
Green beansApr 29–May 20
ZucchiniApr 29–May 13
OkraMay 13–May 27
PeppersMay 6–May 20
BasilApr 29–May 13
Butternut squashApr 29–May 13
CantaloupeMay 6–May 20
EggplantMay 6–May 20
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesMar 25–Apr 8
OnionsMar 11–Apr 1
CarrotsApr 1–May 6
LettuceApr 8–Apr 29
BroccoliMar 25–Apr 8
BeetsMar 25–May 6
PeasMar 11–Mar 25
CabbageMar 25–Apr 8
RadishesMar 18–Apr 29
Brussels sproutsApr 8–Apr 22
SpinachMar 11–Apr 1
CilantroApr 8–Apr 29
KaleMar 25–Apr 8
Collard greensMar 25–Apr 8
TurnipsMar 25–Apr 8
DillApr 22–May 6
CeleryApr 29–May 6
CauliflowerApr 8–Apr 22
LeeksApr 8–Apr 22
Swiss chardApr 8–May 6
ParsleyApr 8–Apr 29
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsOct 8–Nov 12
GarlicOct 1–Nov 5
Daffodil bulbsSep 24–Nov 5
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesMar 25–Apr 8
AsparagusMar 25–Apr 8

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FApr 4Apr 22May 10Oct 7Oct 22Nov 6
Hard freeze, 28°FMar 13Apr 3Apr 21Oct 18Nov 2Nov 17

Read the spring 10% column as the date after which only one year in ten still gets frost. That is the safer date for tomatoes, peppers and basil.

Where these numbers come from

NOAA station Ogden Hinkley Airport (USW00024126) sits 2.6 miles from the center of Roy at 4,470 feet. Its averages cover 1991 to 2020. Low spots, valleys and open fields can keep getting frost a week or two after the station stops; city centers and lakeshores usually get less of it.

Questions

When is the last frost in Roy, UT?

The average last frost date in Roy is April 22, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 10.

When is the first frost in Roy?

The first frost in fall usually comes around October 22. One year in ten it arrives before October 7.

How long is the growing season in Roy?

About 180 days between the average last and first frost.

When should I plant tomatoes in Roy?

Plant tomato seedlings outside from April 29 to May 13. Start seeds indoors six to eight weeks earlier.

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