PIERRE, S.D. (AP) — Quickly deteriorating blizzard conditions have shut down large stretches of two major interstates in South Dakota and led Sioux Falls Regional Airport to close.

The airport will be closed until Saturday night. Several flights have been cancelled.

The Department of Transportation says heavy snow and strong winds are creating zero visibility in some areas. Interstate 90 is closed from Rapid City to Mitchell — a stretch of about 276 miles (444 km) — an area that crosses most of the state.

Interstate 29 is also closed from the North Dakota border to Brookings.

Dozens of school districts canceled classes Friday as snow accumulation is expected to be 12 to 16 inches. Gov. Dennis Daugaard closed many state government offices and several events were postponed, including Brandon Valley High School's prom, which was moved to Sunday.