Hokkaido (5), the 7-5 favorite, won Sunday's first race at the Gulfstream Park West meet at Calder in Miami Gardens,
The race was a $25,000 maiden claimer for 2-YO fillies.
It was scheduled for 7 1/2 furlongs on turf. GP West moved it to seven furlongs on the dirt track, listed as Fast, with hopes of giving the course more time to dry out after recent days' rains.
Skies remain clear, But the Weather Channel forecast is for the chance of rain to increase to 50 percent before 3:00 p.m.
The Rainbow 6 has a carryover of $66,584. The 20 cents per combination-only bet is on races four to nine with the sequence scheduled to start at 1:44 p.m.
Gulfstream has guaranteed that the jackpot for the Rainbow 6 will be at least $125,000 if there is just one ticket with all six winning horses.