Two-thirds of Iowa’s state park beaches faced “swimming not recommended” advisories at least once this summer, with heavy rains fueling higher bacteria levels that pushed advisories to their highest rate in a decade, according to state monitoring officials and data.

The Iowa Department of Natural Resources issued 156 advisories across 39 state beaches, up from 145 advisories last year. That meant about 26% of weekly water samples collected from Memorial Day through Labor Day tested high enough for bacteria or toxins to trigger warnings — the highest advisory rate since at least 2016.

Wet years tend to drive bacteria spikes, while calm, dry summers allow algal blooms to build. Iowa was wetter this year than the past few summers, washing bacteria downstream into Iowa’s lakes and beaches, s

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