Question: Chance of rain today for Daytona?
Answer: 70% (from 50% as of yesterday)
The Weather Channel: "Rain showers early becoming a steady light rain for the afternoon. High 67F. Winds ENE at 10 to 20 mph."

This changes the complexion of the race quite a bit. The 100th lap mark is crucial since that makes the race official. If the race is halted after that because of rain, the leader is likely declared the winner. This means the race is likely go into a hyper mode around and past the 100th lap mark. If there is even a single rain drop or even clouds moving in the wrong direction, watch out -- there should be free for all to be in the front. This makes the race outcome even more volatile and intriguing.

Start: Greg Biffle, Roush Fenway Racing Ford leads the field
Start: Greg Biffle, Roush Fenway Racing Ford leads the field

Photo by: Eric Gilbert

For reference, I discuss the impact of rain on NASCAR racing below and more details are at Rain Free for All.

The NASCAR Sprint Series rarely runs on wet tracks. So following scenarios are possible for the Daytona 500.

Scenario 1: Raining at start time (1 pm EST)
Race will be delayed until rain stops and track can be fully dried. Most likely they will try to run the race that day or evening. If rain doesn't stop or the track cannot be dried that day, then the race will likely be pushed off to the next dry day.

Scenario 2: Rain starts during the first half of the race (less than 100 lap mark for the Daytona 500)
Most likely NASCAR will wave a red flag and cars will be pulled off the track. If rain is very slight then a yellow might be issued to slow down the pace, but this is less likely.

The Goodyear tires are stacked up in the garage area
The Goodyear tires are stacked up in the garage area

Photo by: Motorsport.com / ASP Inc.

Scenario 3: Rain starts after the half way mark and doesn't stop (101 laps and beyond)
NASCAR could stop the race and resume later or call the race official and end the race. The leader at the point of of halt is then deemed the winner. This makes the 100th lap mark particularly important for racers. After this, they have to be ready to take the lead, but at the same time, they have to consider drafting and fuel strategies.

Scenario 4: Use rain tires (treads versus smooth)
This was tried in 2008, but unlikely.