To water your plants on hot days get a carrier bag with holes, make a few more if you need to. Put some ice cubes inside the carrier and then tie the top of the bag in a knot. Then rest the bag of ice on the surface of the pot container/window box first thing in the morning. The heat of the day will slowly melt the ice-cubes and keep your plants watered for longer.
To water hanging baskets – just drop a half dozen ice cubes onto the surface of the soil daily. Because the ice melts slowly, the soil has time to absorb the moisture as needed, without the risk of messy overflow.