Zion National Park is a stunning desert landscape and is one park that is getting relatively crowded even in the winter. In the past 10 years, its visitor numbers have shot up by 35 percent — it is now the sixth-most visited park in America, with more than 4 million people clamoring for a glimpse of its spectacular views. In fact, even winter travelers have been reporting some traffic backups on the road leading to the park [source: Marcus]. The park is so overrun with tourists it's considering requiring reservations to explore its main canyons.
But let's give this some perspective. January and February may see 200,000 visitors altogether. In June and July, those numbers sky rocket to more than 1 million, and you can't even access the park in your vehicle — you're required to hop on a park shuttle instead. In winter, you can actually drive into Zion and take in the great views and wildlife, like mule deer and songbirds. Hiking is also very popular. Just be careful on the roads — they can be icy. The weather can be cold and wet (temps hover in the 50-60s F during the day and below freezing at night). And nearly half the annual precipitation may come between December and March. However, spring can come as early as late February [sources: Christ, Utah.com, NPS].