South Dakota weather and outdoor projects
South Dakota has cold winters and warm summers. Sioux Falls in the east is more humid and gets more summer rain, while Rapid City in the west is drier and sees chinook winds that bring sudden winter warm spells. Wind is common statewide.
June through early September is the most dependable window for staining, painting and concrete. Spring frosts can come into May, and fall frosts in late September. Summer thunderstorms, sometimes with hail, are common in the afternoon, so morning work is safer.
Frost dates in South Dakota
In Sioux Falls, the median last spring freeze (32°F) is around May 1 and the median first fall freeze is around October 6, a frost-free season of about 157 days.
In Rapid City, the median last spring freeze (32°F) is around May 12 and the median first fall freeze is around October 1, a frost-free season of about 139 days.
How South Dakota compares with other states
Sioux Falls has the 5th-most freezing nights of the 50 state main stations (162 a year). Sioux Falls has the 7th-shortest frost-free season of the 50 state main stations (157 days). Sioux Falls is tied for the 10th-most humid summer afternoons of the 47 state main stations (53% humidity at 3 PM, June–August).
| Measure (Sioux Falls) | Value | Rank, highest first |
|---|---|---|
| Deck staining season | 4 good months | 20th of 50 |
| Frost-free season | 157 days | 44th of 50 |
| Freezing nights | 162 a year | 5th of 50 |
| Rainy days | 53 a year with 0.1 in or more | 36th of 50 |
| Days at 90°F or hotter | 15 a year | 37th of 50 |
| Summer afternoons | 53% humidity at 3 PM, June–August | 10th of 47 |
Best time to stain a deck in South Dakota
In Sioux Falls, the most reliable months are June–September. May and October can also work on the right days (average highs May 71°F, Oct 61°F). November–March is too cold, with average highs around 36°F. In April, nights average about 36°F, too cold for the coating to dry and cure overnight. In May, nights average about 48°F, so finish early on mild days and check the overnight low. October is cool, with highs around 61°F, so choose the warmest afternoons.
In Rapid City, the most reliable months are June–August. May and September can also work on the right days (average highs May 67°F, Sep 76°F). November–March is too cold, with average highs around 41°F. In April and October, nights average about 32°F, too cold for the coating to dry and cure overnight. In May and September, nights average about 44°F, so finish early on mild days and check the overnight low.
Best time to paint outside in South Dakota
In Sioux Falls, the most reliable months are May–September. April and October can also work on the right days (average highs Apr 59°F, Oct 61°F). November–March is too cold, with average highs around 36°F. In April and October, nights average about 37°F, so finish early on mild days and check the overnight low.
In Rapid City, the most reliable months are June–September. May and October can also work on the right days (average highs May 67°F, Oct 60°F). November–March is too cold, with average highs around 41°F. In April, nights average about 31°F, too cold for the coating to dry and cure overnight. In May and October, nights average about 38°F, so finish early on mild days and check the overnight low.
Best time to pour concrete in South Dakota
In Sioux Falls, the most reliable months are May–September. October–April averages about 23 nights a month at or below 32°F, so fresh concrete needs blankets or heated enclosures.
In Rapid City, the most reliable months are June–September. May can also work on the right days (average highs May 67°F). October–April averages about 24 nights a month at or below 32°F, so fresh concrete needs blankets or heated enclosures. May brings about 4 freezing nights a month, so pick a mild spell and keep curing blankets on hand.
Best time to seal a driveway in South Dakota
In Sioux Falls, the most reliable months are June–August. May and September can also work on the right days (average highs May 71°F, Sep 76°F). November–April is too cold, with average highs around 40°F. In October, nights average about 38°F, too cold for the coating to dry and cure overnight. In May and September, nights average about 50°F, so finish early on mild days and check the overnight low.
In Rapid City, the most reliable months are July–August. June and September can also work on the right days (average highs Jun 78°F, Sep 76°F). November–April is too cold, with average highs around 44°F. In May and October, nights average about 38°F, too cold for the coating to dry and cure overnight. In June and September, nights average about 49°F, so finish early on mild days and check the overnight low.
Best time to fertilize or treat a lawn in South Dakota
In Sioux Falls, the most reliable months are May–October. April can also work on the right days (average highs Apr 59°F). November–March is too cold, with average highs around 36°F. April is cool, with highs around 59°F, so choose the warmest afternoons.
In Rapid City, the most reliable months are May–June and August–October. April and July can also work on the right days (average highs Apr 57°F, Jul 86°F). November–March is too cold, with average highs around 41°F. April is cool, with highs around 57°F, so choose the warmest afternoons. July is hot, with highs near 86°F, so start early and keep out of full afternoon sun.
How the weather differs across South Dakota
| Place | Hottest month avg high | Coldest month avg low | Rain per year | Last spring freeze | First fall freeze |
|---|---|---|---|---|---|
| Sioux Falls | 85°F | 9°F | 28 in | May 1 | October 6 |
| Rapid City | 86°F | 13°F | 17 in | May 12 | October 1 |
Of the places above, Sioux Falls has the most good months for staining, painting and concrete combined (14 job-months), and Rapid City has the fewest (11).
Monthly weather in Sioux Falls
| Month | Avg high | Avg low | Wet days* | Rain | 3 PM humidity | Freezing nights |
|---|---|---|---|---|---|---|
| January | 27°F | 9°F | 2 | 0.6 in | 69% | 31 |
| February | 32°F | 13°F | 3 | 0.8 in | 63% | 27 |
| March | 45°F | 24°F | 4 | 1.6 in | 54% | 25 |
| April | 59°F | 36°F | 6 | 3.0 in | 45% | 13 |
| May | 71°F | 48°F | 7 | 3.9 in | 47% | 1 |
| June | 81°F | 59°F | 7 | 4.2 in | 50% | 0 |
| July | 85°F | 63°F | 5 | 3.3 in | 53% | 0 |
| August | 83°F | 61°F | 5 | 3.3 in | 55% | 0 |
| September | 76°F | 52°F | 5 | 2.7 in | 48% | 1 |
| October | 61°F | 38°F | 4 | 2.4 in | 47% | 10 |
| November | 45°F | 25°F | 3 | 1.2 in | 55% | 24 |
| December | 32°F | 13°F | 2 | 0.8 in | 66% | 30 |
*Days with 0.1 inch of rain or more; column notes.
Monthly weather in Rapid City
| Month | Avg high | Avg low | Wet days* | Rain | 3 PM humidity | Freezing nights |
|---|---|---|---|---|---|---|
| January | 36°F | 13°F | 1 | 0.3 in | 52% | 30 |
| February | 38°F | 14°F | 2 | 0.5 in | 47% | 27 |
| March | 48°F | 23°F | 2 | 0.9 in | 41% | 26 |
| April | 57°F | 31°F | 5 | 2.1 in | 40% | 16 |
| May | 67°F | 42°F | 7 | 3.5 in | 45% | 4 |
| June | 78°F | 52°F | 7 | 2.9 in | 44% | 0 |
| July | 86°F | 59°F | 5 | 2.3 in | 37% | 0 |
| August | 85°F | 56°F | 4 | 1.6 in | 33% | 0 |
| September | 76°F | 46°F | 3 | 1.2 in | 32% | 1 |
| October | 60°F | 34°F | 3 | 1.4 in | 36% | 13 |
| November | 47°F | 22°F | 1 | 0.5 in | 42% | 26 |
| December | 37°F | 14°F | 1 | 0.3 in | 50% | 30 |
Source: NOAA NCEI U.S. Climate Normals 1991–2020 for SIOUX FALLS, RAPID CITY RGNL AP. See how the ratings work and how late in fall you can stain, paint or seal.
Frequently asked questions
When is the best time to stain a deck in South Dakota?
In Sioux Falls, June–September. In Rapid City, June–August.
When is the last frost in South Dakota?
Sioux Falls: around May 1; Rapid City: around May 12.
Can you pour concrete in winter in South Dakota?
Yes, with cold-weather practices: Sioux Falls averages about 88 freezing nights from December to February, so fresh concrete needs insulated blankets, a heated enclosure or an accelerated mix, and must not freeze in the first 48 hours. Many homeowners wait for spring.
What months are best for sealing a driveway in South Dakota?
In Sioux Falls, June–August. In Rapid City, July–August.