The National Parks Service is helping people celebrate the first day of summer this Tuesday by waiving entrance fee to all national parks for non-commercial vehicles. That certainly includes the world's first national park, says Yellowstone Spokesman Al Nash, so the 25-dollar entrance permit is free.

Entrance fee waived:

"The National Parks Service is waiving entrance fees at all national parks on Tuesday, the 21st of June. It's a way to encourage people to come and enjoy their parks, and what better time to celebrate than the longest day of the year."

And after heavy snow-pack made the clearing of some park roads unusually difficult this year, all park roads are open, says Nash. And he reminds would-be visitors that even though it's the beginning of summer, shorts and flip-flops are optimistic attire in Yellowstone.

Yellowstone climate:

"All of the roads into and around the park are open for the season, finally. Now, the caveat is, remember, we are high elevation, so summer's shorter, it arrives later, and it doesn't necessarily mean it's going to be hot while you're here."

Nash recommends clothing items for temperatures that range from freezing to 80 degrees.