Frogger - Why did the cane toad cross the road?

Remember the old computer game "Frogger"? Released in 1981 by Konami and nowadays regarded as a classic, the object of the game was to try and get frogs to their homes one by one. To do this, each frog had to try and avoid cars while crossing a busy road, and then navigating a river full of hazards.

Think about how many cane toads you see squashed on the road. What time of year do you tend to see them the most? Is it a wet season or a dry season, a warm season or a cold one?
Why do you think they are on the road - are they trying to get to the other side, or are they trying to warm their bodies up on the bitumen that's been heating up in the sun all day?