Oklahoma Frost Dates & Growing Season Guide
Oklahoma (OK) spans USDA hardiness zones 7a, 7b, with growing seasons ranging from 222 days in Oklahoma City to 235 days in Lawton. The average growing season across the state is approximately 227 days.
Oklahoma City Frost Dates
The table below shows the average last spring frost date, first fall frost date, growing season length, and USDA hardiness zone for each city. Click a city name for detailed planting calendars and zone information.
Planting Windows for Oklahoma
Based on average frost dates, here are the recommended planting windows for each city. The indoor seed start date is approximately seven weeks before the last spring frost. Transplanting should occur about two weeks after the last frost. The last direct sow date for fall crops is ten weeks before the first fall frost.
| City | Start Seeds Indoors | Transplant After | Last Direct Sow |
|---|---|---|---|
| Oklahoma City | February 8 | April 11 | August 27 |
| Tulsa | February 6 | April 9 | August 28 |
| Norman | February 5 | April 8 | August 29 |
| Lawton | January 31 | April 3 | September 1 |
Gardening in Oklahoma
Oklahoma's position where the humid East meets the arid West creates a dynamic gardening climate. Eastern Oklahoma receives more rainfall and has slightly longer growing seasons than the drier western plains. The state's 222 to 235 frost-free days support a wide range of warm-season crops. Spring weather is volatile, with the potential for late freezes, hail, and severe storms requiring protective strategies. Oklahoma's alkaline soils benefit from sulfur and organic matter amendments. Summer heat above 100 degrees is routine in July and August, stressing many crops. Heat-tolerant varieties and afternoon shade for sensitive plants help maintain production through the hottest weeks. Fall gardens planted in August provide excellent cool-season harvests.
Understanding Oklahoma's Hardiness Zones
Oklahoma includes USDA hardiness zones 7a, 7b. These zones indicate the average annual extreme minimum winter temperature for each area, which determines which perennial plants, trees, and shrubs can survive winter without protection. When purchasing trees, shrubs, or perennial flowers, always check that the plant is rated for your hardiness zone or a lower (colder) zone number.
Tips for Using Oklahoma Frost Dates
These frost dates represent long-term averages and should be treated as guidelines rather than guarantees. In any given year, the actual last spring frost or first fall frost may arrive one to three weeks earlier or later than the average. Factors that affect your specific location include elevation above the city center, proximity to water, slope direction, and whether you are in an urban or rural area. South-facing slopes and areas near large pavement or building masses tend to be warmer than surrounding open land. Low-lying valleys and exposed hilltops are often colder than mid-slope positions.
To protect against late spring frosts, keep row cover fabric, old bed sheets, or frost blankets on hand. Monitor your local weather forecast daily as the average frost date approaches. When frost is predicted after you have transplanted, covering plants in the late afternoon traps ground heat and can protect against temperatures down to about 28 degrees Fahrenheit. For fall season extension, the same covers protect mature plants from early frosts, often buying several additional weeks of harvest.