Rain will be spreading into Daytona sometime between 1 am and 4 am. It will not be a very heavy rain - not heavy enough to stop the race, I think - and rainfall amounts through sunrise will likely be between a tenth and a quarter inch. Rain will taper off in the mid to late morning, between 9 am and noon. The rain will have moved out before the end of the race, with clouds beginning to decrease.
Use our radar link at the top of the page to follow the rain. I'll try to provide updates on Twitter - @Race4caster - but I won't staying up for the whole night when the rain will be moving in.