| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 2.9° | -8.4° | 7.7mm | 5.9 | 18 |
| February | 3.1° | -8.2° | 13.6mm | 7.3 | 16 |
| March | 8.2° | -3.7° | 24.5mm | 7.7 | 38 |
| April | 13° | 1.1° | 54.3mm | 10.2 | 56 |
| May | 18.3° | 7° | 101.2mm | 14.1 | 66 |
| June | 25.1° | 12.8° | 82.2mm | 13 | 74 |
| July | 29.9° | 16.9° | 63.1mm | 10.9 | 67 |
| August | 28.9° | 15.7° | 54.6mm | 8.9 | 75 |
| September | 24° | 10.9° | 35.9mm | 6.9 | 86 |
| October | 15.4° | 3.6° | 37.7mm | 7.5 | 70 |
| November | 8.8° | -2.5° | 11.5mm | 4.3 | 49 |
| December | 3.3° | -7.5° | 9.5mm | 5.3 | 22 |
January in Rapid City averages a daily high of 2.9°C with nights around -8.4°C. Expect roughly 5.9 wet days totalling 7.7mm. A hard month to visit for comfort alone.
February in Rapid City averages a daily high of 3.1°C with nights around -8.2°C. Expect roughly 7.3 wet days totalling 13.6mm. A hard month to visit for comfort alone.
March in Rapid City averages a daily high of 8.2°C with nights around -3.7°C. Expect roughly 7.7 wet days totalling 24.5mm. Demanding conditions — pack for it and plan indoor options.
April in Rapid City averages a daily high of 13°C with nights around 1.1°C. Expect roughly 10.2 wet days totalling 54.3mm. Generally workable, with some weather to plan around.
May in Rapid City averages a daily high of 18.3°C with nights around 7°C. Expect roughly 14.1 wet days totalling 101.2mm. Generally workable, with some weather to plan around.
June in Rapid City averages a daily high of 25.1°C with nights around 12.8°C. Expect roughly 13 wet days totalling 82.2mm. Generally workable, with some weather to plan around.
July in Rapid City averages a daily high of 29.9°C with nights around 16.9°C. Expect roughly 10.9 wet days totalling 63.1mm. Generally workable, with some weather to plan around.
August in Rapid City averages a daily high of 28.9°C with nights around 15.7°C. Expect roughly 8.9 wet days totalling 54.6mm. Comfortable conditions for being outdoors all day.
September in Rapid City averages a daily high of 24°C with nights around 10.9°C. Expect roughly 6.9 wet days totalling 35.9mm. Comfortable conditions for being outdoors all day.
October in Rapid City averages a daily high of 15.4°C with nights around 3.6°C. Expect roughly 7.5 wet days totalling 37.7mm. Generally workable, with some weather to plan around.
November in Rapid City averages a daily high of 8.8°C with nights around -2.5°C. Expect roughly 4.3 wet days totalling 11.5mm. Demanding conditions — pack for it and plan indoor options.
December in Rapid City averages a daily high of 3.3°C with nights around -7.5°C. Expect roughly 5.3 wet days totalling 9.5mm. A hard month to visit for comfort alone.
Each month scores out of 100. It starts at 100 and loses points for daytime highs outside a 20–27°C band, for wet days, and for nights below 2°C. Nothing else is weighted in — no crowd data, no prices, no opinion. Rapid City peaks at 86.
Based on 30 years of records, September scores highest for comfort in Rapid City, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 29.9°C.
May is the wettest, averaging 101.2mm of rain across roughly 14.1 wet days.
January is the coolest month, with average daily highs around 2.9°C.