Course officials made the straightforward call after having moved forward their intended 8am inspection on raceday morning.
Heavy rain on today put paid to any notion of the fixture being given the green light.
Exeter clerk of the course Barry Johnson said: "It's so frustrating. "We were raceable at 9am this morning, but in the last couple of hours we've had 18 millimetres of rain, with another 50mm forecast today.
"You can't beat the weather, unfortunately."
There will be no racing action in the UK tomorrow as a result of this cancellation.
John Smith's is to end its sponsorship of the Grand National after the 2013 renewal of the race.