"Then you conduct a pitch inspection, preferably in your match boots and with a match ball, and conduct as thorough an examination as possible on every area of the playing surface to try and ensure it is behaving as it should.
"If there is any room for doubt, such as the playing surface being frozen, for example, you find out from the groundsman whether there is anything he can do to solve the problem."
Unfortunately you can't always correctly predict what the weather or the temperature will be like an hour before kick-off, let alone six or seven, and a match might be abandoned in mid-flow.
"On one occasion in April we were out on the pitch in shirtsleeves at 2pm and by ten past three we were in the midst of a snow blizzard," Riley says.
"The players couldn’t see their team-mates and one player collided with an opponent.
"In that instance I had no option but to abandon on two counts: a) I could neither guarantee the safety of the players nor b) guarantee the match as a spectacle because the supporters couldn't see what was going on."
If there is any concern about the ability to play the match the referee will discuss this with the Match Manager, who will liaise directly with the Premier League Match Centre.
This enables the team at the Match Centre to inform fans as quickly as possible via the League's digital channels and announcements by major broadcasters.