BRISTOL, Tenn. - It's no secret that rain can affect driving conditions for any NASCAR race, but Bristol Motor Speedway is especially monitored due to its unique track.
The Food City Dirt Race takes place Sunday in northeast Tennessee's iconic dirt racing facility.
Deep in the dirt, or rather red clay, lies about two inches of sawdust to protect the concrete racing surface of the just over half-mile track.
NASCAR says that it is then topped by 5,330 cubic yards of dirt saved from Bristol's first foray into dirt racing back in 2000-01, followed by 4,008 cubic yards of dirt from the campground as well as lime-treated clay.
BRISTOL, TENNESSEE - MARCH 29: Denny Hamlin, driver of the #11 FedEx Freight Toyota, and Ryan Blaney, driver of the #12 Advance My Track Challenge Ford, lead the field during the NASCAR Cup Series Food City Dirt Race at Bristol Motor Speedway on Marc
With the layers it takes to upkeep the track, VP of Operations for the motor speedway, Steve Swift, says that rain isn't the only thing they monitor.
"We really look at dew points," he says, "The relative humidity really plays a key factor in how much moisture you put on the track to try to get the track sealed off and how much moisture that you need to add throughout the day to get it to be a perfect racetrack."
Knowing the amount of moisture helps crews prepare for races.
"If the humidity levels are really high, then the track gets to be really good. We don't have to add as much water before we started doing dirt on concrete," Swift said.
BRISTOL, TENNESSEE - MARCH 29: Denny Hamlin, driver of the #11 FedEx Freight Toyota, pits during the NASCAR Cup Series Food City Dirt Race at Bristol Motor Speedway on March 29, 2021 in Bristol, Tennessee. (Photo by Chris Graythen/Getty Images)
And it doesn't just come down to the day of conditions. Crews monitor the weather months in advance.
It's the winter and spring months leading up to the race that Swift says get tricky.
"We can get some systems that blow through that can produce snow and cold weather that doesn't tend to dry up," he said.
Ultimately, the moisture in the atmosphere is what matters most on race day.
"It's still science. It's dirt, it's rain, it's water," Swift said. "So, you really can't depend on all those things, but we really play on that humidity."
And even though conditions are expected to be dry to start the race, rain chances increase overnight in Bristol, leading to increased humidity.
NASCAR's Easter Sunday race will be the first time since 1989, when a February race at Richmond was postponed to the holiday.