Haydock© Photo Healy Racing
Haydock's big meeting on Saturday must pass an 8am precautionary inspection on raceday morning.
The Merseyside circuit has sustained 42 millimetres of rain from Wednesday, with 14mm having fallen on Thursday.
There is also the threat of frost, with temperatures likely to drop to minus 2C on Friday night.
The going at Haydock, due to feature four Grade Twos on the card, is currently heavy.