I have never heard about this thought until I read it in Week-by-Week Vegetable Gardener’s Handbook. It make a lot of sense. The book says to use a trash can full of water, but I thing a pitcher of water is all I personal need. Then just let it sit where your seedlings are. This lets the water me the temperature of the room that the seeds are. Then water them with that water. This helps not to shock those little seedlings you have growing.
Follow my garden adventurers on Facebook PA Gardeners