Excessive Heat in Bon Homme, South Dakota

Excessive Heat July 27, 2025 – July 28, 2025 · Bon Homme, South Dakota

What the National Weather Service wrote

Dangerous heat index readings reached an afternoon peak as high as 109 degrees near Tyndall on July 27.

The wider storm

Beneath an expansive and strong, flat ridge aloft, extreme surface-based moisture returned near a diffuse warm frontal boundary on July 26 and lasted into the afternoon of July 28. While this moisture and heat would eventually fuel the derecho during the evening hours of July 28, dangerous heat indices from 105 to 120 degrees were common.

Source: NOAA Storm Events Database, event 1288580. Narratives are written by the National Weather Service forecast office that issued the report.

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