Weather in Sioux Falls in September

Prime time. If you get to pick your dates, September is the one. Highs average 24.6 °C, lows 11.7 °C, and rain falls on 9 days — nothing in the month is working against you.

September is the highest-scoring month of the twelve. The nearest rival is May, and the month at the other end of the year is December.

Rain on 9 days, 2 of them heavy. Enough to need a plan B, not enough to need a plan around it. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: 5 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest September day reached 37.4 °C and the coldest night fell to 0.6 °C, and the wettest single day dropped 72 mm — roughly 94% of the month's rain in one day.

September is moderately variable: 11 mm in the driest year against 142 mm in the wettest, around an average of 77 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 11.9 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 64%.

How September sits in the year

The month is on the way down: 4.3 °C cooler than August, with October dropping another 9.3 °C. The first week and the last are not the same trip.

Daylight in September

12.6 hours of daylight, losing 1.5 hours across the month. That is between Sioux Falls's extremes of 15.4 and 9 hours, so days are long enough not to constrain the plan.

An inland climate

Sioux Falls has no sea to moderate it, and it shows: 43 °C separates the hottest afternoon of the year from the coldest night. That is a genuinely continental range, and it means summer and winter here are barely the same place.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

September in Sioux Falls versus nearby

If Sioux Falls is one option among several, the nearby comparison is worth making. Omaha is close enough to be a coin toss — within a degree on temperature, 1 day more rain. Minneapolis is close enough to be a coin toss — within a degree on temperature, 1 day more rain.

So: September is the answer for Sioux Falls. If it is booked out or priced out, May is the next best thing at 6 points behind, and December is the month to keep off the shortlist.

Every month in Sioux Falls

See all twelve months in Sioux Falls, or where else to go in September.