- Search & compare the best car hire deals
- Free 48-hour cancellation policy & no hidden charges
- Check prices with Avis, Europcar, Sixt & more
Keystone weather in September 2025
Expect 73°F daytime maximum temperatures in the shade with on average 9 hours of sunshine per day in Keystone in September. Check more long-term weather averages for Keystone in September before you book your next holiday to South Dakota in 2025/2026.
- 7373°F max day temperature
- 9 hours of sunshine per day
- 88 days with some rainfall
- 4343°F min night temperature
- 1212 hours of daylight per day
- 0No heat & humidity
- 1.31.3 inches of monthly rainfall
- 66 (High) UV index
More about Keystone
- Overview
- Best time to visit
- Weather by month
- 5-day weather forecast
- Destinations
- Travel advice
- Deals & discounts
Keystone by month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Recommended for South Dakota
The September weather guide for South Dakota (Keystone) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.
Metric (°C) | Imperial (°F)
More about the USA
How hot is it in Keystone in September?
Daytime temperatures usually reach 73°F in Keystone in September, falling to 43°F at night.
How sunny is it in Keystone in September?
There are normally 9 hours of bright sunshine each day in Keystone in September - that's 68% of daylight hours.
Does it rain in Keystone in September?
There are usually 8 days with some rain in Keystone in September and the average monthly rainfall is 1.3 inches.
Keystone September sunrise & sunset times
Browse the sunrise and sunset times for Keystone in September 2025. Select a month to view Keystone sunrise and sunset times for the next 12 months.
JanFebMarAprMayJunJulAugSepOctNovDec
Date | Sunrise times | Sunset times |
---|---|---|
Monday, 1st September 2025 | 05:17 | 18:29 |
Monday, 15th September 2025 | 05:33 | 18:03 |
Tuesday, 30th September 2025 | 05:51 | 17:36 |
Be inspired
Get your weekly fix of holiday inspiration from some of the world's best travel writers plus save on your next trip with the latest exclusive offers
We promise not to share your details
Related posts
Popular travel offers
Explore holidays in the sun for less
- Beach holidays
- Family holidays
- City breaks
- Summer holidays
- Winter sun holidays
- Holiday offers
- Top travel brands
- Airlines & flights
- Discount hotels
- Airport parking deals
- TUI
- Jet2holidays
- easyJet holidays
- Love Holidays
- Black Friday sales
Airport parking
- Manchester Airport
- Stansted Airport
- Bristol Airport
- Luton Airport
- Birmingham Airport
- Edinburgh Airport
- Gatwick Airport
- Glasgow Airport
- Newcastle Airport
Airport lounges
- Manchester Airport
- Birmingham Airport
- Bristol Airport
- Edinburgh Airport
- Glasgow Airport
- Heathrow Airport
- Newcastle Airport
- Stansted Airport
- Gatwick Airport