Thursday's meeting at Wincanton must pass an 8am precautionary inspection on raceday morning.
Although the Somerset circuit is raceable, course officials are taking no chances.
Overnight temperatures are set to drop to minus 2C, but the inspection has been called in case the frost is sharper than has been forecast.
Clerk of the course Barry Johnson said: "I'm very confident we'll be fine - we'll be OK with minus 2C - but some forecasts are predicting minus 4C.
"There's no frost in the ground now, but the ground is quite wet. It's very much a precautionary inspection."
Leicester's meeting on Thursday is also subject to an 8am precautionary inspection in the morning.
Frost is the main issue at the track, with temperatures set to drop to as low as minus 5C.
A maximum daytime temperature of 2C on Thursday has also been forecast.
Clerk of the course Jimmy Stevenson said on Wednesday morning: "There's no frost whatsoever this morning - we are perfectly raceable - but there is quite a severe frost forecast tonight.
"If we think we have a chance at 8am, we'll probably call another inspection later in the morning and then, possibly, look again. We've got to be patient."
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27 August 2015Tested passes with flying colours
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