# Hot water on a cold windshield? **URL:** \ **Category:** Factual Questions\ **Created:** [October 8, 2009, 12:55am UTC](https://boards.straightdope.com/t/hot-water-on-a-cold-windshield/513001 "2009-10-08T00:55:10Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [October 9, 2009, 2:41pm UTC](https://boards.straightdope.com/t/hot-water-on-a-cold-windshield/513001/21 "2009-10-09T14:41:51Z")
> [@FluffyBob](#): > > **As a Canadian I am surprised someone would use hot water to clear ice off a windshield**. Seems a lot of bother, if no ice scraper is handy, a cd, or cassette case case or any thing with 2+ inches of edge (preferably plastic) will do the trick. Start the car, set it to defrost and crank the fan, scrape your window and go. If its truly cold start your car five minutes before you have to leave. There seem to be a lot dependencies to this. An iced windshield at 30 degrees F is a far, far cry from the same at 30 degrees F. From my experience, you can safely pour warmish hot (NOT boiling) water all over the 30 degree windshield with reckless abandon. I’ve got many dings and stars in my windshield, and never have come close to getting a crack from pouring the hot water to remove ice. Now then – I am in Louisiana, and it’s uncommon to wake up to weather colder than the high twenties with ice on the windshield (the rare part is the temperature after sunrise being so low, not the presence of windshield ice). What happens much more often is that the overnight low will be something like 25-30 degrees F, but the morning drivetime temperature will have risen to about the mid thirties. Because of the humidity, ice commonly deposits on windshields in the dark of night, and is still there in the hour or two after sunrise. Perhaps if the ice is already slowly melting, it’s ever so much safer to our the hot water on it … maybe the ice isn’t “gripping” the windshield so tightly. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [October 9, 2009, 2:45pm UTC](https://boards.straightdope.com/t/hot-water-on-a-cold-windshield/513001/22 "2009-10-09T14:45:01Z")
I use just slightly tepid water - not even really warm. I’ve never had any cracking problem, but we don’t get really cold weather here in southern England (lowest overnight mins are usually around 20F a few times a year). If using tepid water, you need to leave the wipers going once the frost has melted, otherwise it will refreeze. ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [October 9, 2009, 2:50pm UTC](https://boards.straightdope.com/t/hot-water-on-a-cold-windshield/513001/23 "2009-10-09T14:50:33Z")
> [@t-bonham@scc.net](#): > > We were astonished … that they ever had to scrape ice from their windshields in Alabama … If we have to get ice off our windshields in New Orleans, they certainly have to in Alabama, as well. I’d expect northern Alabama to get quite cold, actually. Not Minnesota cold, but probably getting down around 10-12 F at some point every winter. ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [October 9, 2009, 2:51pm UTC](https://boards.straightdope.com/t/hot-water-on-a-cold-windshield/513001/24 "2009-10-09T14:51:45Z")
Missed the Edit window. In post #21 above: An iced windshield at 30 degrees F is a far, far cry from the same at **30 degrees F.** is supposed to read: An iced windshield at 30 degrees F is a far, far cry from the same at \*\*0 degrees F. \*\* ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [October 9, 2009, 2:54pm UTC](https://boards.straightdope.com/t/hot-water-on-a-cold-windshield/513001/25 "2009-10-09T14:54:36Z")
> [@Colophon](#): > > I use just slightly tepid water - not even really warm. I’ve never had any cracking problem, but we don’t get really cold weather here in southern England (lowest overnight mins are usually around 20F a few times a year). I am betting that as long as whatever you’re doing doesn’t vaporize the ice instantly, the risk of cracking is minimal. Also, there seems to be a sweet spot temperature-wise (circa 25-35 F) where gentle melting is possible without rapid re-freezing. ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [October 9, 2009, 3:08pm UTC](https://boards.straightdope.com/t/hot-water-on-a-cold-windshield/513001/26 "2009-10-09T15:08:17Z")
Okay, ahead and ordered the thing. I can’t help it. My name is mangeorge, and I am a gizmo addict. So, I’ll install it and sound the alarm here if it cracks my windshield within the next couple years. If it works good, maybe I’l post my excitement in MPSIMS. Bub Eye mangeorge ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [October 9, 2009, 3:22pm UTC](https://boards.straightdope.com/t/hot-water-on-a-cold-windshield/513001/27 "2009-10-09T15:22:20Z")
Handy if you ever need a hot shower while out on the open road, I suppose. 🙂 ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [October 9, 2009, 5:30pm UTC](https://boards.straightdope.com/t/hot-water-on-a-cold-windshield/513001/28 "2009-10-09T17:30:35Z")
> [@Colophon](#): > > Handy if you ever need a hot shower while out on the open road, I suppose. 🙂 Also handy if you just want to get in the car, start it up and clear some light icing from your windshield and not have to play Nanook of the North. [Previous page](https://boards.straightdope.com/t/hot-water-on-a-cold-windshield/513001.md?page=1)