How Crowded Is Effigy Mounds National Monument in September?

September runs about 1.2× Effigy Mounds National Monument's average month, which makes it a busy month here — roughly 10% of the park's yearly visitors come in September.

In a typical September the park sees roughly 5,900 recreation visits, based on National Park Service monthly counts from 1979 to 2025.

That makes September the 5th-busiest of the park's twelve months, sitting between the July peak (2×) and the December low (0.4×).

On our Best Time to Visit score September rates 62/100 ("Good"), versus the top-rated May at 63/100 — pleasant weather with noticeably thinner crowds (shoulder season).

Typical September weather, from 1991–2020 NOAA climate normals at the nearest station, averages a daytime high near 74°F and an overnight low around 52°F, with about 4" of precipitation.

That average of about 63°F is a comfortable range for hiking and being outdoors all day.

Because June, July and August together draw about 42% of annual visitors, choosing September instead steps outside that summer crush — the single biggest lever on how crowded the park feels.

You'll have about 12.3 hours of daylight in September to explore — between the 8.8-hour midwinter low and the 15.2-hour summer high.

Park-wide, 2025 drew 56,912 recreation visits, down 8.2% from 61,975 in 2024.

Across the past decade overall visitation has risen about 7.1%, so a September visit is likely to feel busier than it did a few years ago.