Excessive Heat — Hanson, South Dakota

2025-06-20 to 2025-06-22 · Hanson, South Dakota

Event narrative

Daily afternoon and evening heat indices ranged from 105 to 112 degrees with a maximum heat index of 112 degrees at the Road Weather Information System site near Alexandria on June 20.

Wider weather episode

The upper-level pattern experienced amplification of an eastern U.S. ridge and western U.S. trough, which locked a low-level frontal boundary in place from western Nebraska through central South Dakota into the Great Lakes. This allowed for heat to spread northward as very high dew point readings pooled across the area with the recent wet conditions. This multi-day dangerous heat event featured daytime heat index readings from 100 to 120 degrees, with nighttime low temperatures remaining from the mid 70s to lower 80s.

Source: NOAA Storm Events Database, event_id 1277857. Narrative written by the NWS forecast office that issued the report.