USDA Hardiness Zone 5a
Frost Dates for 57702 — Rapid City, South Dakota
NOAA 1991–2020 normals from Johnson Siding, SD (4,184 ft), 5 miles northwest.
Updated
In Rapid City, the last spring frost (32°F) is around May 20 in half of years and has passed by June 3 in nine years out of ten. The first fall frost comes around September 25, as early as September 11 one year in ten, leaving a typical freeze-free season of 126 days (NOAA, Johnson Siding, SD).
- Last spring frost
- May 20
- First fall frost
- September 25
- Growing season
- 126 days
- Hardiness zone
- 5a
50% probability
50% probability
freeze-free, 50%
-20 to -15°F (-28.9 to -26.1°C) coldest night
- First snow
- October 23
- Last snow
- April 25
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
16 of 16 observed
NOAA normal
Frost risk by date in Rapid City
Half of springs at Johnson Siding, SD see their last 32°F night by May 20; only one in ten is past it by May 9, and one in ten still has one after June 3. Planting tender crops after May 26 leaves a 30% risk of a frost on them, after May 29 20%, and after June 3 10%. The 14 days between the even-odds date and the one-in-ten date is wider than at 59% of the 49 South Dakota stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 25 in half of years, as early as September 11 one year in ten, and holds off past October 7 one year in ten. A hard freeze of 28°F follows 9 days later, around October 4; in spring the one-in-ten date for 28°F is May 22, 12 days before the 32°F one. The freeze-free season lasts 126 days in a typical year, shorter than at 98% of the 49 South Dakota stations; it reaches 145 days one year in ten and falls short of 107 one year in ten. On average 190 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 13 days longer, to about June 2, and return around September 15. Severe cold of 16°F or below comes every winter, usually between October 31 and April 5.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 19 | May 24 | May 27 | May 30 | Jun 2 | Jun 5 | Jun 8 | Jun 13 | Jun 18 |
| 32°F | May 9 | May 13 | May 15 | May 18 | May 20 | May 23 | May 26 | May 29 | Jun 3 |
| 28°F | Apr 25 | Apr 30 | May 2 | May 5 | May 8 | May 10 | May 13 | May 17 | May 22 |
| 24°F | Apr 12 | Apr 17 | Apr 21 | Apr 24 | Apr 27 | Apr 29 | May 1 | May 4 | May 9 |
| 20°F | Apr 1 | Apr 6 | Apr 9 | Apr 12 | Apr 15 | Apr 18 | Apr 22 | Apr 25 | Apr 30 |
| 16°F | Mar 18 | Mar 25 | Mar 30 | Apr 2 | Apr 5 | Apr 8 | Apr 11 | Apr 15 | Apr 21 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 1 | Sep 6 | Sep 9 | Sep 12 | Sep 15 | Sep 17 | Sep 20 | Sep 23 | Sep 27 |
| 32°F | Sep 11 | Sep 16 | Sep 20 | Sep 22 | Sep 25 | Sep 28 | Sep 30 | Oct 3 | Oct 7 |
| 28°F | Sep 21 | Sep 25 | Sep 29 | Oct 1 | Oct 4 | Oct 6 | Oct 9 | Oct 13 | Oct 17 |
| 24°F | Sep 29 | Oct 3 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 20 | Oct 23 | Oct 27 |
| 20°F | Oct 8 | Oct 13 | Oct 17 | Oct 20 | Oct 22 | Oct 25 | Oct 28 | Nov 1 | Nov 6 |
| 16°F | Oct 15 | Oct 21 | Oct 25 | Oct 29 | Oct 31 | Nov 3 | Nov 6 | Nov 10 | Nov 15 |
Freeze probabilities 1991–2020 at Johnson Siding, SD, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 57702 →Compare Rapid City with another place →
Weather by month in Rapid City
July is the warmest month at Johnson Siding, SD, averaging 83°F by day and 54°F at night; January is the coldest at 39°F and 12°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, June still brings one in 14% of years.
Warmth for growing adds up to 1,904 growing degree days a year (base 50°F), the fewest of the 49 South Dakota stations. 26% of them (490) have built up by the end of June, and July adds the most, 567. Precipitation totals 21.7 inches a year, most in May (4.2") and least in January (0.4"); May to September bring 68% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 39 | 12 | 0.4 | 100% | 31 | 0 |
| Feb | 39 | 14 | 0.5 | 100% | 28 | 0 |
| Mar | 48 | 21 | 0.9 | 100% | 28 | 5 |
| Apr | 55 | 29 | 2.4 | 100% | 20 | 25 |
| May | 64 | 39 | 4.2 | 98% | 7 | 119 |
| Jun | 75 | 47 | 3.6 | 14% | <1 | 342 |
| Jul | 83 | 54 | 3.5 | 0% | 0 | 567 |
| Aug | 81 | 52 | 2.1 | 0% | 0 | 515 |
| Sep | 73 | 43 | 1.4 | 70% | 3 | 274 |
| Oct | 59 | 32 | 1.6 | 100% | 16 | 54 |
| Nov | 48 | 21 | 0.6 | 100% | 27 | 5 |
| Dec | 40 | 14 | 0.5 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Johnson Siding, SD (4,184 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Rapid City 4NW, SD, 6 miles northeast of Rapid City and 705 feet lower, has a last frost 10 days earlier (May 10), a first frost 10 days later (October 5), a season 21 days longer.
When it snows in Rapid City, South Dakota
The first measurable snow (0.1 inch or more) in Rapid City usually arrives around October 23, and the last of the season around April 25. Those are the middle dates across the winters of 1991–2020 at Johnson Siding, SD, 5 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 25 days after the last snow.
Planting calendar for 57702
| When | What to do |
|---|---|
| March 11 – March 25 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 25 – April 8 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 22 – May 6 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 20 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 3 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 11 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 25 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 57702 is 5 miles from Johnson Siding, SD, which stands at 4,184 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 57702 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across South Dakota →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.