Do Windshield Frost Covers Work?
This lesson draws on FrostGuard’s instructions and two versions of its FAQ, the National Weather Service, a review on The Gadgeteer and a Jeep owner’s forum report. How we research explains the method.
Why a parked car frosts over
Frost can show up even when the forecast low stays above freezing. The National Weather Service office in Louisville explains that official temperatures are measured about 6.6 ft (2 m) above the ground, and on a clear, calm night the air near the ground can be 5 or more degrees Fahrenheit (about 3 degrees Celsius) colder. That’s why frost can appear when the official low is in the upper 30s Fahrenheit (about 3-4°C).
So a forecast of 37°F (3°C) doesn’t mean a clear windshield in the morning. A cover works by putting a layer between the glass and the open sky and falling snow, so the frost and snow land on the cover instead of the windshield. You then lift the cover off, and the glass under it is clear.
What a cover does and doesn’t do
FrostGuard’s FAQ says its cover protects the essential viewing area of the front windshield, and its instructions say the perimeter edges may not be covered. The FAQ also says it’s designed for the front windshield only. In the manual, elastic loops go over the side mirrors and a security panel is shut inside the driver’s door.
What it won’t do:
- Side and rear windows still need scraping. The Gadgeteer’s reviewer found the windshield clear while the side windows were frosty.
- Edges of the windshield can still frost.
- Driving with it on is off limits. FrostGuard says it’s only for parked cars and warns against using it as a sunshade or in very hot weather.
Wind, damp glass and freezing rain
Fit matters most. FrostGuard says a cover that’s too large sits loose and lets moisture and wind reach the glass, and that the fit should be taut and flat so gusts can’t get underneath. The Gadgeteer’s reviewer saw the top edge lift during strong gusts, though the cover never came off, and the door panel helped hold it down.
FrostGuard’s instructions also say to apply it over a dry windshield for best results. The Gadgeteer’s reviewer didn’t get to test snow or freezing rain, and guessed that wind-driven precipitation could get under the cover.
A Jeep owner on JLwranglerforums.com says a FrostGuard worked very well on his wife’s TJ and took about 2 minutes to put on. On his wider JL he cut down the side poles of a FrostGuard Plus to make it fit, and notes that, unlike a beach towel, it doesn’t soak up water and frost.
When a cover is worth it
A cover makes the most sense if your car sits outside on clear, cold nights and you leave early. It turns a full windshield scrape into pulling off a sheet and leaves only the side and rear windows.
It’s less useful if you park in a garage, if your mornings bring freezing rain more than frost, or if you’d rather run the defroster for a few minutes anyway.
Pick the size for your windshield. FrostGuard’s 2020 FAQ gives 59 x 41 in (150 x 104 cm) for Standard, meant for compact cars, small sedans and small SUVs, and 68 x 41 in (173 x 104 cm) for X-Large, meant for minivans, medium and large SUVs and large pickups. Its 2016 FAQ listed widths of 61 in (155 cm) and 70 in (178 cm), measured at the base, so check the size chart for the exact model before you buy.
FrostGuard Plus Windshield Cover
A cover for the front windshield and wipers, with security panels, side poles and two mirror covers. For parked cars only. Pick the size for your windshield.
Key specs
- Standard: 59 x 41 in (150 x 104 cm)
- XL: 68 x 41 in (173 x 104 cm)
- Front windshield only, parked use only
Paid link
View on Amazon (opens in a new tab)You still need a scraper for the side windows and the uncovered edges. A snow brush with a built-in scraper also clears snow off the roof and lights.
Snow Joe SJBLZD Telescoping Snow Broom
A telescoping snow broom with a foam head and a built-in ice scraper, for clearing snow off the roof, windows and lights and scraping the side windows.
Key specs
- Foam broom head
- Telescoping handle
- Built-in ice scraper
Paid link
View on Amazon (opens in a new tab)For the rest of the winter kit, see the roadside emergency kit checklist.
