"It's too cold to play with the water."
It's not toasty, but this is not why I'm refusing to let them fill a bucket and then splash it all over the deck (and the towels we have to cover the tiles with so that they don't turn into a slip-hazard). I can't be bothered doing the laundry. I can't be bothered changing the kids in and out of clothes and togs, and then mopping puddles off the floor.
I'm lazy, but sure, I'll blame the weather.