Frost Dates
Frost Dates · South Dakota

Frost dates for Sioux Falls, South Dakota

South Dakota · first & last freeze, from NOAA 1991–2020 climate normals

Typical last spring freeze (32°F)
April 26
median date, 1991–2020
Typical first fall freeze (32°F)
October 13
median date, 1991–2020
Typical frost-free season
170 days
between the median dates

In a typical year, the last spring freeze around Sioux Falls comes near April 26 and the first fall freeze near October 13. One year in ten, a freeze still arrives after May 9 in spring — and one year in ten, the first fall freeze has already landed by September 28. NCEI's own growing-season statistic (days between freezes, percentiled per year) puts the median at 169 days.

JFMAMJJASONDApril 26October 13
The year at a glance: blue bands span the 9-in-10 to 1-in-10 range where the last spring / first fall 32°F freeze lands; the green band is the typical frost-free window between the median dates. Measured at Sioux Falls Wfo Ap, SD (USC00397666), 3.2 mi from the city's census reference point, elev. 1,430 ft. NOAA/NCEI 1991–2020 normals.

Freeze-date probabilities, three thresholds

ThresholdLast spring — 9 in 10 years past byLast spring — typical (median)Last spring — 1 in 10 years later thanFirst fall — 1 in 10 years byFirst fall — typical (median)First fall — 9 in 10 years by
36°F — near-freezing (frost can occur)April 23May 6May 19September 20October 2October 16
32°F — freezingApril 10April 26May 9September 28October 13October 28
28°F — hard freezeApril 2April 15April 30October 11October 24November 6

Measured at Sioux Falls Wfo Ap, SD (USC00397666), 3.2 mi from the city's census reference point, elev. 1,430 ft. NOAA/NCEI 1991–2020 normals. Read each date column as odds over the 30-year record — e.g. "9 in 10 years past by" means only one spring in ten saw a later freeze than that date.

Frost-free windows (computed)

Window (32°F ends)OpensClosesLength
Cautious (1-in-10 freeze risk at each end)May 9September 28142 days
Typical (median freeze dates)April 26October 13170 days
Gambler's (9-in-10 freeze risk at each end)April 10October 28201 days

Pure arithmetic on the freeze-date percentiles above — the "cautious" window opens on the date only 1 year in 10 still sees a later spring freeze, and closes on the date by which only 1 year in 10 has already frozen.

About this city's numbers