Seed Starting Calendar for Utah

Count back from the median last frost where you garden. At Salt Lake City (Salt Lake City Intl Airport) that date is April 8, so for spring 2027 onions start indoors Dec 31 to Jan 14, peppers Feb 11 to Feb 25 and tomatoes Feb 18 to Mar 4. Across Utah's 163 NOAA stations the median last frost runs from Apr 3 to Jun 11 for the middle 90 percent, so a garden near Brian Head starts later than one near Hite Ranger Station.

It depends on the station. The earliest median last spring freeze in Utah is March 9 at Hite Ranger Station; the latest is June 21 at Brian Head. A median is a coin flip: at Salt Lake City the last 32°F freeze comes after April 8 in half of years, and has passed by April 30 in 9 of 10 years (NOAA 1991 to 2020 normals).

UNH Extension sets tomatoes out 1 to 2 weeks after the last frost, which at Salt Lake City is Apr 15 to Apr 22 in 2027. Tomatoes are frost tender, so the date to watch is April 30, when 9 of 10 springs at Salt Lake City have had their last 32°F night. Hardening off starts two weeks before setting out (Apr 1 to Apr 15).

Utah State University Extension publishes planting months by region (Beaver, Castle Dale, Cedar City, Coalville, Duchesne, Farmington, Fillmore, Heber, Kanab, Laketown, Loa, Logan - SW Farm, Logan - USU, Manila, Manti, Marysvale, Midvale, Moab, Monticello, Morgan, Nephi, Ogden, Panguitch, Price, Provo - BYU, Provo - Airport, Richfield, Salt Lake Int'l Airport, Salt Lake County- Cottonwood Weir, Santaquin, St George, Tooele, Tremonton, Vernal, West Jordan Conservation Garden, Woodruff). For Beaver, tomatoes go in during June. Seeds for transplants go in 4 to 10 weeks ahead of those months, depending on the crop.

Utah State University Extension's Suggested Vegetable Planting Dates for Utah puts it this way: "Many vegetables are easier to grow using transplants that are started indoors several weeks before planting outdoors." The guide is linked below with the date it was read (September 21, 2026).

UNH Extension gives 8 to 10 weeks from seed to transplant for both, and sets peppers out 2 weeks after the last frost and eggplant 2 to 3 weeks after, so the sowing date is 6 to 8 weeks before the median last frost. At Salt Lake City that is Feb 11 to Feb 25 for peppers.

About two weeks. University of Missouri Extension: "Hardening should be started about two weeks before planting in the garden." University of Minnesota Extension adds that seedlings should go out on a cloudy day or in the late afternoon.

St. George in Dixie reaches its median last frost around Mar 14, Salt Lake City around Apr 8, Moab around Apr 22, and Logan in Cache Valley around May 8. Each station carries its own dates: St. George Mar 14 and Logan May 8 at the median.