Utah Frost Dates & Growing Season Guide
Utah (UT) spans USDA hardiness zones 5a, 6b, 7a, 8b, with growing seasons ranging from 95 days in Park City to 242 days in St. George. The average growing season across the state is approximately 169 days.
Utah 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.
| City | Last Spring Frost | First Fall Frost | Growing Season | Zone | Min Temp |
|---|---|---|---|---|---|
| Salt Lake City | April 25 | October 15 | 173 days | 7a | 0°F |
| Provo | April 28 | October 10 | 165 days | 6b | -5°F |
| St. George | March 15 | November 12 | 242 days | 8b | 15°F |
| Park City | June 5 | September 8 | 95 days | 5a | -20°F |
Planting Windows for Utah
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 |
|---|---|---|---|
| Salt Lake City | March 7 | May 9 | August 6 |
| Provo | March 10 | May 12 | August 1 |
| St. George | January 26 | March 29 | September 3 |
| Park City | April 17 | June 19 | June 30 |
Gardening in Utah
Utah's dramatic elevation range creates vastly different growing environments within a compact area. St. George in the southwestern corner at zone 8b has a 242-day season, while Park City at nearly 7,000 feet in zone 5a has just 95 frost-free days. Salt Lake City at 4,226 feet sits in a moderate zone 7a with 173 days. Utah's alkaline soils, low humidity, and limited rainfall make drip irrigation and mulching essential. The state's intense sunshine and low humidity produce minimal fungal disease pressure, which is a significant advantage. Tomatoes, peppers, squash, melons, and herbs thrive in the warm valleys. High-elevation gardens focus on root crops, greens, and short-season varieties. Fruit trees need careful late-frost protection as warm spring days often precede freezing nights.
Understanding Utah's Hardiness Zones
Utah includes USDA hardiness zones 5a, 6b, 7a, 8b. 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 Utah 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.