The part of racing in the rain: Procedures, rain-tire info for damp forecast at Roval

The threat of rain looms over this weekend's races for the NASCAR Cup Series and Xfinity Series at the Charlotte Motor Speedway Roval. Remnants from Hurricane Delta are expected to have a drenching effect on the 2.28-mile circuit for the Saturday-Sunday doubleheader. RELATED: Charlotte Roval weekend schedule | Roval 101 Since it's a road-course venue, teams will have rain tires at the ready should conditions allow for wet-weather racing. With drivers bracing for the uncertain possibility of competing in Mother Nature's adverse conditions on one of stock-car racing's trickiest layouts, it's time for a review of the procedures, information and other fast facts for NASCAR's version of racing in the rain. Race rules and procedures In the event of inclement weather, each series' race director can declare a "wet" start or "damp" start, according to the NASCAR Rule Book. A wet start means that the entire racing surface is covered in moisture; a damp start means that the track has areas of moisture, but that other areas are dry. The race director can also declare the conditions not race-ready, if heavy downpours cause puddles and impaired visibility. For a wet weather start:

• All vehicles must mount rain tires, activate their rear flashing light and have a working windshield wiper installed.
• Normal starting procedures follow.

For a damp weather start:

• All vehicles may elect to install rain tires at the crew chief's discretion. The rear flashing light must be activated, and windshield wipers may be installed.
• Any team making a pit stop for rain tires on subsequent pace laps will forfeit their starting spot.

After the green flag, teams are permitted to change tires -- to treaded rain tires or dry-weather slicks -- at the crew chief's discretion. RELATED: Drivers on potential to race in the rain at Charlotte Goodyear rain tires NASCAR Cup Series teams will each have four sets of Goodyear wet-weather tires available for their 109-lap race Sunday. Xfinity Series teams will have two sets of rain tires each for Saturday's 67-lapper. The rain tires have a distinctive tread pattern to channel away water as opposed to the treadless dry-weather slicks that each series normally uses. The rain tires also feature white Goodyear lettering on the sidewalls instead of the customary yellow. Weather outlook Charlotte Motor Speedway's forecast calls for a 70 percent chance of precipitation for Saturday's Xfinity Series' Drive for the Cure 250 (3:30 p.m. ET, NBC/NBC Sports App, PRN, SiriusXM NASCAR Radio) and an 80 percent chance for Sunday's Cup Series' Bank of America Roval 400 (2:30 p.m. ET, NBC/NBC Sports App, PRN, SiriusXM NASCAR Radio), according to the National Weather Service. Sunday's forecast includes the possibility of thunderstorms, in which case a lightning strike within eight miles of the speedway would force a 30-minute hold. For further updates, please check NASCAR.com/weather for at-track conditions and hourly forecasts. Rain-racing history The Xfinity Series has been the most affected of NASCAR's three national tours, having raced in wet-weather conditions seven times -- all since 2008. Those include two instances this season -- Aug. 8 at Road America and then briefly at the start of the Daytona Road Course event one week later. The Cup Series conducted two feasibility tests for rain tires in 1995 (Watkins Glen, Martinsville) and has only used wet-weather Goodyears in practice and qualifying since. Teams qualified in the rain for a Japanese exhibition race in 1997, then used rain tires during a practice session at Watkins Glen in 2000. Part of the Cup Series' lone race at Road America in 1956 was conducted in the rain, but the cars were not equipped with special wet-weather tires.