Sunday's meetings at Exeter and Hereford both face inspections before they can be given the go-ahead.
Exeter, which is raceable at present, will stage a precautionary 8am inspection on raceday due to the threat of frost as sub-zero temperatures are forecast for the next two nights.
Hereford are checking at 11.30am on Saturday following rain and a mild night in an attempt to give the fixture every chance, although the forecast is not favourable.
Exeter clerk of the course Barry Johnson said: "We had no frost on Thursday night and we had rain rather than snow. We've called a precautionary inspection to keep everyone ahead of the game.
"It could be minus 4C on Friday and Saturday night, but the daytime temperatures give us a chance. It depends how quick the temperature rises."
At Hereford, clerk of the course Keith Ottesen said: "It didn't drop below zero all night and we had rain, not snow, which helped shift most of the frozen areas, although there are still a few frozen patches.
"It could be a false dawn as it is supposed to be very cold on Friday night, but we couldn't call it off now. It rests on how cold it gets tonight really."
