Rain may well play a factor in tonight's Coca-Cola 600 at Charlotte Motor Speedway (FOX, 5:30 p.m. ET).

And if it does, NASCAR's longest race might not go the full distance after all.

As of 8:30 a.m. ET, weather.com says there's only a 20 percent change of rain at 6 p.m., which is good. But as the night goes on, the chance of rain increases, with showers predicted to begin around 9 p.m.

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For the race to become official, the drivers will have to get to one lap past the halfway point, which means 201 laps, or 301.5 miles. If the forecast is accurate, that should be doable, although it could change team strategy.

Still, teams don't know if they'll go the full distance tonight, shorter than the full distance or race on Monday if rain washes out the race. It makes planning difficult, at best.

"I think the biggest question is whether we'll race (tonight) or Monday," said pole-sitter Martin Truex Jr. "I think going from day to night is not that huge of a deal, you can kind of just band aid things for the day and hang on to it planning on trying to be good at nighttime.

"Then if you have that game plan and you have to race in the daytime then you're going to have to band aid it for the whole race and then your chances of winning are probably not good. I don't know, it's a tough one. We're just trying to figure it all out right now, but we'll see what happens."

FOXSports.com will have weather updates throughout the day.