I've used warm water for years. My 'defrost kit' is a couple of plastic milk cartons. I just sling 'em behind the drivers seat or in the boot, so no need to go back in the house with a kettle or watering can.
I just use tepid or warm water, and the colder the weather the cooler the water. There are sufficient anecdotes found on tinternet to convince me that hot or boiling water just isn't worth the risk.
I just use tepid or warm water, and the colder the weather the cooler the water. There are sufficient anecdotes found on tinternet to convince me that hot or boiling water just isn't worth the risk.