Those are 8 mile hexes, so if you forced March, you could make it 3 hexes at a normal pace or nearly 4 at a fast pace (penalty to wis checks) for clear hexes. Mountains/forest I would consider difficult terrain (1/2 speed), hills or light woods would be half difficult (3/4 speed). Does that seem fair? The rules only really account for difficult and open so 3/4 speed is made up and wanted to make sure it made sense.