DENVER -- The Colorado Department of Transportation said it could be the most significant traffic event of the year.
Hundreds of thousands of vehicles are expected to begin traveling this weekend through Colorado to Wyoming and Nebraska for Monday's total solar eclipse.
Traffic was heavy on I-25 in the Fort Collins area by midday Saturday.
The path of totality will cross through both states and they are considered the best viewing areas in the country for the first coast-to-coast solar eclipse in 99 years.
The message from CDOT is to leave as early as possible and to not wait until Monday.
The Colorado State Patrol is expecting a major increase from New Mexico through Colorado up to Wyoming and Nebraska -- more than any holiday weekend.
Potentially up to 500,000 extra vehicles are expected to impact Interstates 25 and 76, and U.S. Highways 85 and 287.
Denver will have about 92 percent totality late Monday morning, but several hundred thousand people will be trying to get into the 70-mile wide path of complete totality.
"If you want to reach it to the path of totality, either leave in the days prior or very early on Monday," Colorado State Patrol Major Tim Keeton said.
"It’s not a very long drive in normal traffic conditions, but I don’t expect us to be in normal traffic conditions.
"Have water, have preps, have snacks, have the ability to sit for a long time. Have a full tank of fuel."
Cell service might be limited so the Colorado State Patrol is recommending travelers bring paper maps.
Also, gas stations will be few and far between -- and they'll likely be packed.
The Colorado State Patrol will have extra troopers on the highways. There will be tow trucks and ambulances along the main routes.
CDOT is also halting construction during the weekend along the eclipse routes.
RELATED: Map shows what solar eclipse will look like across the country
RELATED: Interactive map of how the eclipse will look
RELATED: Where to see the solar eclipse
RELATED: What the solar eclipse will look like by ZIP code
RELATED: How to make a DIY solar eclipse viewer at home
RELATED: What not to do during a solar eclipse
RELATED: Tips for taking photos of solar eclipse
RELATED: Avoid buying bogus eclipse glasses