The park spans 750,000 acres across elevations from 2,000 to 13,000 feet, which means conditions change dramatically within miles. A sunny morning in the valley can turn to afternoon thunderstorms in the high country. Winter brings heavy snow to the peaks while the valley floor stays relatively mild. Spring runoff can flood the valley floor, creating mirror-still reflections and temporary closures. Plan your activities around the season, check road conditions before you drive, and pack layers for whatever the day brings.