Excessive Heat — Union, South Dakota

2025-08-15 to 2025-08-17 · Union, South Dakota

Event narrative

Dangerous heat index values peaked as high as 109 degrees at North Sioux City and 101 degrees 4 miles south of Beresford on August 16.

Wider weather episode

Heat and moisture pooled near and south of a nearly stationary frontal boundary across eastern South Dakota and southern Minnesota. Daily highs were in the mid 80s to lower 90s with dew point values in the upper 70s to lower 80s, yielding heat index values from 100 to 115 degrees.

Source: NOAA Storm Events Database, event_id 1291156. Narrative written by the NWS forecast office that issued the report.