Motorists faced hazardous driving conditions in Hull and East Riding early on Monday after up to 5cm (2in) of snow fell overnight.
Commuters awoke to icy roads and a covering of snow which continued to fall across the region.
A yellow weather warning is in place and the Met Office said more snow would continue to fall, but would gradually ease later in the day.
East Riding of Yorkshire Council said gritters have been operating around the clock.
Local authorities reported that 17 schools had been closed for the day due to snow.
The Yorkshire Ambulance Service said it was expecting to see a "marked increase in weather-related slips, trips and falls and road traffic collisions."
Schools closed included Driffield Infants; Driffield Senior; The Market Weighton School; Barmby-on-the-Marsh Primary; Garton-on-the-Wolds Primary; Hutton Cranswick Primary; Kings Mill School; Langtoft School; North Newbald Primary; Sledmere Primary; The Snaith School; Warter Primary and Wetwang Primary. Driffield Junior School was alerting parents that the school may open later.
