There is a strong correlation between the temperature and the number of skinned knees on playgrounds. does this tell us that warm weather causes children toâ trip?

Correlation does not equal causation. It could play some sort of role. Does it say, if the temperature is warm more kids happen to skin their knees? Or just that temperature has some kind of correlation? It's possible cold weather could freeze water on the ground and make it slippery which causes kids to fall over more. That would be the opposite of that statement.

So, short answer: Not necessarily.