My buddy went to Crater Lake for fourth of July back in 1988, and he has a picture of fresh snow on the small island on Crater Lake.
Yes higher elevations are very cold in the late spring. I went to Grand Canyon for Thanksgiving in 1987, the first big trip with my F-350 and camper, that did not have a bathroom or furnace or water heater. It was really cold, with 1/2" of ice on the roads, 2" of snow, and so much fog that I could not see the canyon either. Went back to Laughlin NV, and it was warm enough for shorts and a t-shirt at 950' elevation on the Colorado River.
Great memories. .
Fred..