Last frost date in Watertown, SD

Average last frost
May 7

Expect the last frost in Watertown around May 7. Frost after May 20 happens in only one year out of ten. The first fall frost usually arrives about September 30, which leaves 145 frost-free days. An early freeze before September 19 happens one year in ten.

Safe after (10% risk)
May 20
Average first frost
Sep 30
Frost-free season
145 days
Hard freeze (28°F) ends
Apr 29
Next 7 nights in Watertown

Frost likely Mon night, low 32°F

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

  1. ThuOct 2257°
  2. FriOct 2355°
  3. SatOct 2437°
  4. SunOct 2533°possible frost
  5. MonOct 2632°frost
  6. TueOct 2735°possible frost
  7. WedOct 2837°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost May 7First frost Sep 30145 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND145 frost-free days
Frost risk through the year at Watertown Regional Airport, 0.4 miles from Watertown.

Planting calendar for Watertown

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

Start indoorsPlant outSow outdoorsFall plantingAverage last and first frost
Warm-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
TomatoesMay 14–May 28
PumpkinsMay 21–Jun 4
SunflowersMay 7–May 28
CucumbersMay 21–May 28
CornMay 14–May 28
Sweet potatoesMay 28–Jun 11
WatermelonMay 21–Jun 4
Green beansMay 14–Jun 4
ZucchiniMay 14–May 28
OkraMay 28–Jun 11
PeppersMay 21–Jun 4
BasilMay 14–May 28
Butternut squashMay 14–May 28
CantaloupeMay 21–Jun 4
EggplantMay 21–Jun 4
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesApr 9–Apr 23
OnionsMar 26–Apr 16
CarrotsApr 16–May 21
LettuceApr 23–May 14
BroccoliApr 9–Apr 23
BeetsApr 9–May 21
PeasMar 26–Apr 9
CabbageApr 9–Apr 23
RadishesApr 2–May 14
Brussels sproutsApr 23–May 7
SpinachMar 26–Apr 16
CilantroApr 23–May 14
KaleApr 9–Apr 23
Collard greensApr 9–Apr 23
TurnipsApr 9–Apr 23
DillMay 7–May 21
CeleryMay 14–May 21
CauliflowerApr 23–May 7
LeeksApr 23–May 7
Swiss chardApr 23–May 21
ParsleyApr 23–May 14
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsSep 16–Oct 21
GarlicSep 9–Oct 14
Daffodil bulbsSep 2–Oct 14
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesApr 9–Apr 23
AsparagusApr 9–Apr 23

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FApr 26May 7May 20Sep 19Sep 30Oct 13
Hard freeze, 28°FApr 14Apr 29May 11Sep 26Oct 9Oct 22

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 Watertown Regional Airport (USW00014946) sits 0.4 miles from the center of Watertown at 1,748 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 Watertown, SD?

The average last frost date in Watertown is May 7, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 20.

When is the first frost in Watertown?

The first frost in fall usually comes around September 30. One year in ten it arrives before September 19.

How long is the growing season in Watertown?

About 145 days between the average last and first frost.

When should I plant tomatoes in Watertown?

Plant tomato seedlings outside from May 14 to May 28. Start seeds indoors six to eight weeks earlier.

Nearby in South Dakota

All 5 cities in South Dakota