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Frost dates for Mtn Dell Dam, Utah

Half of years have their last spring frost by May 7 — but 1 year in 10 still frosts after May 27.

Every other site gives you one date. A frost date is not a date: it is a percentile from 30 years of records at a nearby weather station, and planting to the median means losing the crop in half of years. Both numbers are below, so you can choose the risk yourself.

The odds

Last spring frost

Frost this late in 1 year in 10
May 27
1 year in 5
May 17
3 years in 10
May 13
2 years in 5
May 9
Half of years (the median)
May 7

First fall freeze

Freeze this early in 1 year in 10
September 29
1 year in 5
October 3
3 years in 10
October 6
2 years in 5
October 11
Half of years (the median)
October 14
Growing season
about 158 days
Hardiness zones nearby
5b, 6a, 6b, 7a, 7b

Where these numbers come from

NOAA NCEI 1991–2020 Climate Normals, station Mtn Dell Dam (USC00425892), at 40.75, -111.72. These are that station's own records, unshifted. The further your garden is from it, the less exactly they describe your ground — the planner resolves the nearest station to your own ZIP and lowers its confidence with distance, rather than presenting one number as if it were measured in your yard.

Cold air also pools in low ground on the clear, still nights when frost happens, so a hollow can freeze while a slope a hundred metres away does not. No table can know that about your garden. Your own logged frosts eventually can.

ZIP codes nearest this station

84010, 84014, 84025, 84033, 84047, 84054, 84070, 84087, 84092, 84093, 84094, 84098, 84101, 84102, 84103, 84105, 84106, 84107, 84108, 84109, 84111, 84112, 84113, 84115, 84117, 84119, 84121, 84123, 84124, 84144, 84180.

What can I plant here, and when? →

Nearby stations

The nearest stations, and how their last-frost dates compare — the frost gradient across your area, which no single station shows.

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