Sandown's jumps meeting on Saturday is under threat from frost with an inspection called for 8am on Friday.
Although the track has been covered there is evidence of frozen ground in a few places.
Sandown director of racing Andrew Cooper said: "We need to be taking stock of where we've got to. There is frozen ground in a few places under the covers as of today, not significant, but enough to raise alarm bells."
He added: "They are not going to shift that readily and with another cold night forecast let's see what that brings and take it from there."
Wetherby officials are crossing their fingers they miss the worst of the predicted frost ahead of Saturday's meeting featuring the totepool.com Towton Novices' Chase.
"We've had a virtual frost-free week except for a couple of hours around daybreak today where it dipped to minus 1C, but it's what is going to come that is the problem," said clerk of the course Jonjo Sanderson.
"There's nothing to inspect at this stage. We will just have to see what happens."
Ffos Las are pulling out all the stops to stage their big fixture on Saturday, highlighted by the Welsh Champion Hurdle.
Clerk of the course Tim Long said: "We're doing everything that we can.
"Although we are due another frost on Thursday night, if the Met Office forecast for a weather front with rain later on Friday is correct then we've got a good chance."
