That includes all 63 national parks and more than 420 places in total.

The first free day is coming up on Monday, January 16, which is Martin Luther King Jr. Day.

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The free January day is a great time weatherwise to visit national parks that are blazin' hot in summer -- think Death Valley National Park in California, Big Bend National Park in Texas and Everglades National Park in Florida.

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But given how popular the parks have become, it might be a good idea to plan early, arrive early and check online for potential timed entries on the free days.

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That's especially true for the most popular parks with comfortable temperatures in January.

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For instance, visitation to Big Bend is up 50% since 2016, according to the NPS.

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Its primary visitor season is October through April. You don't want to head out on the free day and be flummoxed by long lines.

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"National parks are really amazing places and we want everyone to experience them," said  National Park Service Director Chuck Sams in the NPS news release about the free days.

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That includes all 63 national parks and more than 420 places in total.

That includes all 63 national parks and more than 420 places in total.

The first free day is coming up on Monday, January 16, which is Martin Luther King Jr. Day.

The first free day is coming up on Monday, January 16, which is Martin Luther King Jr. Day.

The free January day is a great time weatherwise to visit national parks that are blazin' hot in summer -- think Death Valley National Park in California, Big Bend National Park in Texas and Everglades National Park in Florida.

The free January day is a great time weatherwise to visit national parks that are blazin' hot in summer -- think Death Valley National Park in California, Big Bend National Park in Texas and Everglades National Park in Florida.

But given how popular the parks have become, it might be a good idea to plan early, arrive early and check online for potential timed entries on the free days.

But given how popular the parks have become, it might be a good idea to plan early, arrive early and check online for potential timed entries on the free days.

That's especially true for the most popular parks with comfortable temperatures in January.

That's especially true for the most popular parks with comfortable temperatures in January.

For instance, visitation to Big Bend is up 50% since 2016, according to the NPS.

For instance, visitation to Big Bend is up 50% since 2016, according to the NPS.

Its primary visitor season is October through April. You don't want to head out on the free day and be flummoxed by long lines.

Its primary visitor season is October through April. You don't want to head out on the free day and be flummoxed by long lines.

"National parks are really amazing places and we want everyone to experience them," said National Park Service Director Chuck Sams in the NPS news release about the free days.

"National parks are really amazing places and we want everyone to experience them," said National Park Service Director Chuck Sams in the NPS news release about the free days.

"National parks are really amazing places and we want everyone to experience them," said  National Park Service Director Chuck Sams in the NPS news release about the free days.

"National parks are really amazing places and we want everyone to experience them," said  National Park Service Director Chuck Sams in the NPS news release about the free days.