During most years, the North Rim access road and facilities (lodge, campground, etc.) don't open until around May 15. They don't plow the road in the winter. The elevation is quite high (8,000 - 9,000ft.). So, snow tends to linger well into May in a typical year.
Originally Posted by Lee Shively
I have no idea if this winter has been "typical". Best to call the park and inquire on the expected road opening date if you'd like to visit before mid-May.
The South Rim is a much longer drive from points north, but is open year round.