Duncan, OK planting zone & frost dates

Duncan is in USDA hardiness zone 8a. The last spring frost usually comes around March 25 and the first fall frost around November 7, for a growing season of about 225 days.

USDA hardiness zone8aavg. extreme winter low 10°F to 15°F

Average last spring frostMarch 2590% chance of no frost after April 12

Average first fall frostNovember 710% chance of frost by October 22

Growing season225 daysfrost-free days in an average year

Planting calendar for Duncan

Dates are counted from the average last spring frost (March 25) 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: Jan 28 – Feb 11 Transplant outdoors: Apr 1 – Apr 8
Peppers	Start seeds indoors: Jan 14 – Jan 28 Transplant outdoors: Apr 8 – Apr 15
Eggplant	Start seeds indoors: Jan 14 – Jan 28 Transplant outdoors: Apr 8 – Apr 15
Broccoli	Start seeds indoors: Jan 14 – Jan 28 Transplant outdoors: Feb 25 – Mar 11
Cabbage	Start seeds indoors: Jan 14 – Jan 28 Transplant outdoors: Feb 25 – Mar 11
Onions (sets)	Plant outdoors: Feb 25 – Mar 11
Peas	Sow outdoors: Feb 11 – Feb 25
Spinach	Sow outdoors: Feb 11 – Feb 25
Lettuce	Sow outdoors: Feb 25 – Mar 11
Carrots	Sow outdoors: Feb 25 – Mar 11
Potatoes	Plant outdoors: Feb 25 – Mar 11
Beans	Sow outdoors: Apr 1 – Apr 8
Sweet corn	Sow outdoors: Apr 1 – Apr 8
Cucumbers	Sow outdoors: Apr 1 – Apr 8
Squash & zucchini	Sow outdoors: Apr 1 – Apr 8
Basil	Start seeds indoors: Feb 11 – Feb 25 Transplant outdoors: Apr 1 – Apr 8

Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Sep 12 (8 weeks before the average first fall frost on Nov 7).

Useful for zone 8a 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

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Frost risk in detail

	90% chance	50% chance	10% chance
Last 32°F frost in spring is after	Mar 3	Mar 25	Apr 12
First 32°F frost in fall is before	Nov 23	Nov 7	Oct 22

How to read it: in spring there is a 10% chance of a frost after April 12, so that is a safe date for tender plants. In fall there is a 10% chance of frost before October 22. A hard freeze (28°F) usually ends around March 11.

Hardiness zone by ZIP code in Duncan

73533 zone 8a
73534 zone 8a
73536 zone 8a

Nearby cities

Lawton zone 7b, last frost Apr 1
Chickasha zone 7b, last frost Apr 4
Ardmore zone 8a, last frost Mar 15
Norman zone 7b, last frost Mar 31
Mustang zone 7b, last frost Apr 4
Moore zone 7b, last frost Apr 4
Yukon zone 7b, last frost Apr 2
El Reno zone 7b, last frost Apr 6

All cities in Oklahoma → · Other zone 8a cities →

Questions

What growing zone is Duncan, OK?

Duncan is in USDA Plant Hardiness Zone 8a (average extreme winter low 10°F to 15°F), according to the USDA 2023 map.

When is the last frost in Duncan?

The average last spring frost (32°F) in Duncan is March 25. There is still a 10% chance of frost until April 12.

When can I plant tomatoes in Duncan?

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

Frost dates: NOAA U.S. Climate Normals 1991–2020, station Duncan, OK (USC00342660), 0.2 km (0.1 mi) from the city center, elevation 343 m, based on 21 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.