What is weather like in Yellowstone National Park in late September???

Not a meteorologist but it’s been my experience that September can go either way. The second weekend in September most of the stores and facilities start to close. The nights are definately getting cooler. Expect anything from 80s during the day to snow.

One thing to keep in mind is that the park is very different from one area to the next. We’ve had snow at Old Faithful and driven north to Mammoth to clear blue, sunny skies!

Best advise anyone can give is to pack for any situation. Warm clothes for snow and shorts for warm temps.

Fall is beautiful with the leaves turning and the elk bugling. The bear activity will also be high this year. They start looking to gorge themselves for the winter starting in August.