New Englander here - windshield wiper fluid will defrost your windshield in about 20 seconds. Problem solved.

Generally speaking, frost forms when the temperature is below freezing and meets the dew point (relative humidity = 100%). It's the high relative humidity that results in either condensation (dew, when it's above freezing) or deposition (frost, when it's below freezing).

If the temperature is below freezing, but the dew point is even lower (low relative humidity), frost isn't likely to form.

There are details like wind and cloud cover that can make a difference when it's close, but you can get a pretty good idea by checking the forecast for both the temperature and dew point (or relative humidity).

Anonymous wrote:Put a beach towel across your windshield. Pull it off in the morning. No frost on the glass.

This.

Put a beach towel across your windshield. Pull it off in the morning. No frost on the glass.

Maybe operating a motor vehicle isn't for you, OP.

But yes. A good scraper on a long stick and it's a minute to clear.

Frost will be in things that were wet before it got cold. If you car was dry and no dew on condensation, no frost

Use a scraper.

For example, both yesterday and today were very cold. Yesterday? No frost at all on my car. Today? Car was covered in thick frost, and it took me a good 10 minutes to warm up enough to see out of my windows.

Explain it to me like I'm 5, so I can better plan my time in the mornings.