Climate averages 1991–2020
Rapid City weather
in May.
A mild, wet month: the 5th warmest and the wettest of the year.
Long-term climate patterns, not a forecast for a particular trip.
May is a mild month in Rapid City: daytime highs average 18.4°C and nights cool to about 7.2°C. By daytime temperature it is the 5th warmest of the 12 months.
Expect about 112 mm of rain on roughly 14 days, which makes May a wet month (the wettest month of the year). Daylight, from sunrise to sunset, lasts about 14 h 44 min on an average May day.
The nearest other city in this atlas is Bismarck (358 km away). In May its highs average 18.4°C, about as warm as Rapid City, with 73 mm of rain.
Among the 498 cities listed in the United States, Rapid City ranks joint 466th of 498 for the warmest May highs and joint 410th of 498 for the driest May (rainfall, lowest first). The mean May high of those 498 cities is 23.8°C; Rapid City is 5.4°C cooler than that mean.
From May to June, average highs rise by 6.0°C to 24.4°C, and monthly rainfall falls from 112 mm to 97 mm.
The annual picture
May in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Rapid City climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 2.5°C-8.1°C | -8.1°C | 13 | 3.9 | 9.39 h |
| February | 3.5°C-7.6°C | -7.6°C | 20 | 5.1 | 10.410 h |
| March | 8.5°C-3.5°C | -3.5°C | 40 | 7.6 | 11.912 h |
| April | 12.8°C1.1°C | 1.1°C | 80 | 11.8 | 13.413 h |
| May, selected | 18.4°C7.2°C | 7.2°C | 112 | 14.1 | 14.715 h |
| June | 24.4°C12.9°C | 12.9°C | 97 | 14.5 | 15.415 h |
| July | 28.9°C16.9°C | 16.9°C | 78 | 13.4 | 15.115 h |
| August | 28.2°C16.1°C | 16.1°C | 60 | 10.8 | 14.014 h |
| September | 23.3°C11.2°C | 11.2°C | 42 | 6.7 | 12.613 h |
| October | 14.9°C3.9°C | 3.9°C | 50 | 7.3 | 11.011 h |
| November | 7.9°C-2.5°C | -2.5°C | 20 | 4.4 | 9.710 h |
| December | 2.8°C-6.9°C | -6.9°C | 15 | 3.6 | 9.09 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
May in nearby cities
- Bismarck in MayUnited States · 358 kmHigh 18.4°C · Low 7.3°C · 73 mm rain
- Fort Collins in MayUnited States · 417 kmHigh 19.5°C · Low 5.6°C · 87 mm rain
- Greeley in MayUnited States · 424 kmHigh 22.0°C · Low 7.7°C · 67 mm rain
- Loveland in MayUnited States · 437 kmHigh 19.7°C · Low 5.6°C · 87 mm rain
- Billings in MayUnited States · 456 kmHigh 19.6°C · Low 7.0°C · 65 mm rain
- Longmont in MayUnited States · 462 kmHigh 19.9°C · Low 5.9°C · 87 mm rain
- Boulder in MayUnited States · 482 kmHigh 19.2°C · Low 5.1°C · 103 mm rain
- Thornton in MayUnited States · 490 kmHigh 19.6°C · Low 5.3°C · 82 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Rapid City) is explained once on the Rapid City year overview and on the Sources, method and limits page.