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SUS Farms · Utah Gardening
Frost dates by elevation
season · beginner · ~4 min read
In Utah, latitude barely matters compared to elevation. Park City and St. George sit at almost the same parallel, but Park City's last frost is June 15 and St. George's is March 25 — almost three months apart. A useful rule: every 1,000 feet of elevation gain pushes last-frost date about two weeks later in spring and two weeks earlier in fall.
How to find your local date
The Utah Climate Center (climate.usu.edu) maintains 30-year climate normals for nearly every weather station in Utah. Search for your nearest town. Use the 50% probability date as your "average" last frost, and the 90% date as your "safe" date for tender transplants.
Microclimates matter
Within a single yard, a south-facing brick wall can be a full zone warmer than the lawn 30 feet away. Cold air drains downhill at night — low spots frost first. Black plastic mulch warms soil 5–8°F. Floating row cover adds another 4–6°F at night. We use both stacked at our farm to push tomato planting two weeks earlier than the calendar would say.
Fall frost is sneakier
First fall frost is often a one-night event followed by two more weeks of warm weather. Cover the tomatoes with sheets that night, you can usually buy 14 more days of ripening. We track the 14-day forecast in early September religiously.