Jackson, WY planting zone & frost dates

Jackson is in USDA hardiness zone 4b. The last spring frost usually comes around June 20 and the first fall frost around August 31, for a growing season of about 70 days.

USDA hardiness zone4bavg. extreme winter low -25°F to -20°F

Average last spring frostJune 2090% chance of no frost after July 9

Average first fall frostAugust 3110% chance of frost by August 12

Growing season70 daysfrost-free days in an average year

Planting calendar for Jackson

Dates are counted from the average last spring frost (June 20) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.

Crop	When
Tomatoes	Start seeds indoors: Apr 25 – May 9 Transplant outdoors: Jun 27 – Jul 4
Peppers	Start seeds indoors: Apr 11 – Apr 25 Transplant outdoors: Jul 4 – Jul 11
Eggplant	Start seeds indoors: Apr 11 – Apr 25 Transplant outdoors: Jul 4 – Jul 11
Broccoli	Start seeds indoors: Apr 11 – Apr 25 Transplant outdoors: May 23 – Jun 6
Cabbage	Start seeds indoors: Apr 11 – Apr 25 Transplant outdoors: May 23 – Jun 6
Onions (sets)	Plant outdoors: May 23 – Jun 6
Peas	Sow outdoors: May 9 – May 23
Spinach	Sow outdoors: May 9 – May 23
Lettuce	Sow outdoors: May 23 – Jun 6
Carrots	Sow outdoors: May 23 – Jun 6
Potatoes	Plant outdoors: May 23 – Jun 6
Beans	Sow outdoors: Jun 27 – Jul 4
Sweet corn	Sow outdoors: Jun 27 – Jul 4
Cucumbers	Sow outdoors: Jun 27 – Jul 4
Squash & zucchini	Sow outdoors: Jun 27 – Jul 4
Basil	Start seeds indoors: May 9 – May 23 Transplant outdoors: Jun 27 – Jul 4

Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Jul 6 (8 weeks before the average first fall frost on Aug 31).

Useful for zone 4b gardens

Seed starting kit with dome — to start seeds indoors before the last frost
LED grow light for seedlings — stops leggy seedlings
Frost cloth / plant covers — for late spring and early fall frosts
Soil thermometer — warm-season crops need soil above 60°F
Cold frame / mini greenhouse — adds weeks to a short season

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Frost risk in detail

	90% chance	50% chance	10% chance
Last 32°F frost in spring is after	Jun 5	Jun 20	Jul 9
First 32°F frost in fall is before	Sep 13	Aug 31	Aug 12

How to read it: in spring there is a 10% chance of a frost after July 9, so that is a safe date for tender plants. In fall there is a 10% chance of frost before August 12. A hard freeze (28°F) usually ends around June 2.

Hardiness zone by ZIP code in Jackson

83001 zone 4b
83002 zone 4b

Nearby cities

Evanston zone 5a, last frost Jun 12
Riverton zone 4b, last frost May 12
Rock Springs zone 5a, last frost May 24
Sheridan zone 5a, last frost May 21
Casper zone 5a, last frost May 10
Gillette zone 5a, last frost May 15
Laramie zone 4a, last frost Jun 7
Cheyenne zone 5b, last frost May 14

All cities in Wyoming → · Other zone 4b cities →

Questions

What growing zone is Jackson, WY?

Jackson is in USDA Plant Hardiness Zone 4b (average extreme winter low -25°F to -20°F), according to the USDA 2023 map.

When is the last frost in Jackson?

The average last spring frost (32°F) in Jackson is June 20. There is still a 10% chance of frost until July 9.

When can I plant tomatoes in Jackson?

Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Jun 27 – Jul 4. Start seeds indoors 6–8 weeks before the last frost.

Frost dates: NOAA U.S. Climate Normals 1991–2020, station Moose, WY (USC00486428), 19.7 km (12.2 mi) from the city center, elevation 1964 m, based on 16 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.