Sioux City, Iowa – Dense valley fog is creating hazardous driving conditions across parts of western Iowa early Wednesday, with visibility dropping to a quarter-mile or less near river valleys.
According to the National Weather Service in Sioux Falls, dense fog formed overnight due to recent rainfall south of I-90, combined with light winds and clear skies. The fog is most concentrated in low-lying areas, especially near the Little Sioux River and around cities like Cherokee, Ida Grove, and Mapleton. Visibility issues are expected to last through 8 a.m. CDT.
Drivers along U.S. 20, Highway 59, and portions of I-29 should reduce speed and increase following distance, particularly near Sioux City, Onawa, and Missouri Valley. Morning commuters are urged to use headlights and prepare for rapidly changing visibility conditions that may not appear on all weather apps or GPS.
This valley fog pattern is common after rainfall in early summer but can be deceptive, especially before sunrise. Law enforcement may respond to minor accidents in the affected zones, so non-essential travel should be delayed if possible.
The fog should lift shortly after 8 a.m., but visibility may remain spotty in sheltered areas. No additional advisories are expected unless conditions worsen.
