Officials at Plumpton have called an inspection for 8am ahead of Monday's meeting at the East Sussex venue.
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The going on the hurdle course is described as soft, heavy in places with the chase course soft.
Twelve millimetres of rain had been recorded at 2.30pm on top of five millimetres overnight.
Clerk of the course Mark Cornford said: "The rain has been falling here for longer than I expected today, and it hasn't stopped.
"It is expected to fall until 6pm, there might be some drizzle afterwards, but I just need a few dry hours to get rid of the surface water.
"The ground is raceable and hopefully it will stay dry so I can make an early decision tomorrow, but if it keeps raining then I might be having to make the decision the other way."