Haydock's Thursday evening card was abandoned because of waterlogging after an early-morning inspection.
A further 10mm of overnight rain left conditions unraceable at the Merseyside track, which had already been badly hit by the downpours of the past week.
Both Nottingham and Yarmouth, also subject to inspections, were both passed fit to race.
Almost 90mm of rain has fallen at Nottingham since Monday, leaving areas of standing water in the public enclosures a primary concern.
The meeting will go ahead at Colwick Park, however, with an eight-race card set to get under way at 1.40pm on ground described as heavy, soft (in places).
Yarmouth also passed its inspection, after just 5mm of further overnight rain, and conditions for a seven-race card starting at 2.20pm are heavy.
Uttoxeter became the second card lost to waterlogging, however, on Thursday.
The Staffordshire course reported more than 100mm of rainfall in the past six days, including 30 in the previous 24 hours, confirming the abandonment shortly before 7.30am.