Weather Blog: Why does frost form?

Where frost develops depends on the objects temperatures and/or humidity(moisture) level.

Posted: Jan 22, 2021 2:16 PM

FORT WAYNE, Ind. (WFFT) — As it turns colder (again), the potential for frost creeps back into the picture.

Sometimes frost can form on a car but there isn’t any on the ground and sometimes the opposite happens where frost is on the ground but not on your car.

SIGN UP FOR OUR NEWSLETTER

Download the FOX 55 Severe Weather Center App on Apple

Download the FOX 55 Severe Weather Center App on Android 

But, why is that?

Where frost develops depends on the objects temperatures and/or humidity(moisture) level.

Frost can form when the air temperature is below 32 degrees and the ground temperature is freezing.

The temperature that you see on TV or on your phone is actually measured a few feet above the ground and the coldest air is sitting at the surface.

Cold air is more dense which is why it is typically found on the ground or on grassy surfaces.

If the surface temperature is sitting at 32 degrees, frost can still form if the air temperature is 34 degrees.

Another factor is that grass holds moisture which can help frost form.

The burning question might be, but why is there frost on my car and not the grass.

Materials such as metal and glass actually cool down more efficiently than other materials.

For instance, if your car is outside during the day, it’ll heat up under the sun along with the ground.

Once the sun goes down, the car is made of materials that release heat more quickly.

So the windshield and metal could drop to 32 degrees or colder faster than the ground and air around it.

This is why you may see frost on the windshield and nothing on the ground if the air temperature is above freezing.

So why doesn’t frost form on the road or sidewalks?

That also boils down to the fact that concrete holds heat better due to the material it is made of and it cannot hold moisture.

Indiana Coronavirus Cases

Data is updated nightly.

Cases: 947918

Reported Deaths: 15377
CountyCasesDeaths
Marion1291181990
Lake635721103
Allen53899761
Hamilton44082449
St. Joseph42122590
Elkhart33803491
Vanderburgh30574449
Tippecanoe26915251
Johnson23727418
Hendricks22410342
Porter21832347
Clark17562231
Madison17492385
Vigo16302285
Monroe14545191
LaPorte14389239
Delaware14183222
Howard13971273
Kosciusko11498135
Hancock10935166
Warrick10737178
Bartholomew10635170
Floyd10514208
Wayne10077226
Grant9213204
Morgan8928160
Boone8463111
Dubois7791123
Dearborn769490
Henry7691133
Noble7466101
Marshall7409128
Cass7219118
Lawrence7026153
Shelby6647111
Jackson661386
Gibson6190107
Harrison609386
Huntington604495
Montgomery5853105
DeKalb581091
Knox5535104
Miami548888
Putnam543268
Clinton537465
Whitley529354
Steuben501768
Wabash488692
Jasper483861
Jefferson474492
Ripley457777
Adams446068
Daviess4231108
Scott409165
Clay394957
White393858
Greene393392
Wells389884
Decatur388797
Fayette378578
Posey362341
Jennings356056
Washington334747
LaGrange325175
Spencer321136
Fountain318455
Randolph317190
Sullivan309449
Owen287064
Starke282864
Fulton280454
Orange277859
Jay257038
Perry254152
Carroll245229
Franklin242838
Rush237030
Vermillion235050
Parke221420
Tipton212055
Pike211740
Blackford170534
Pulaski168551
Crawford147318
Newton145845
Benton143916
Brown135846
Martin130217
Switzerland126910
Warren115616
Union98511
Ohio80511
Unassigned0482

Ohio Coronavirus Cases

Data is updated nightly.

Cases: 1390015

Reported Deaths: 21820
CountyCasesDeaths
Franklin1541781574
Cuyahoga1361632341
Hamilton989691326
Montgomery681371161
Summit569981051
Lucas51769869
Butler48139663
Stark42350983
Lorain32165539
Warren30497338
Mahoning27564643
Clermont26081297
Lake24873422
Delaware22600147
Licking20818246
Fairfield20789223
Greene20667275
Trumbull20378516
Medina20178290
Clark18235332
Richland16749236
Portage16442231
Wood15973209
Allen14405261
Miami14063261
Muskingum12976155
Wayne12234244
Columbiana12046242
Tuscarawas11248271
Marion10935150
Pickaway10642129
Scioto10585127
Erie9888171
Ross9648177
Lawrence8967125
Hancock8637143
Ashtabula8509187
Geauga8272156
Belmont8262188
Jefferson7736175
Huron7566131
Union743951
Washington7396126
Athens712065
Sandusky6984135
Darke6884137
Knox6839122
Seneca6533137
Ashland6078115
Auglaize596888
Shelby5845104
Brown578272
Mercer565890
Crawford5591117
Defiance5579101
Madison552171
Highland550982
Fulton543583
Clinton535781
Logan520587
Preble5123111
Putnam4909107
Guernsey487664
Williams469982
Perry464454
Champaign454964
Ottawa443584
Jackson436663
Pike400745
Morrow398251
Coshocton393669
Fayette385053
Adams371575
Hardin367570
Gallia356658
Holmes3326111
Henry331869
Van Wert321471
Hocking312370
Wyandot286058
Carroll267052
Paulding247443
Meigs223042
Monroe193149
Noble174442
Morgan170329
Harrison161741
Vinton141919
Unassigned05
Fort Wayne
Partly Cloudy
66° wxIcon
Hi: 88° Lo: 62°
Feels Like: 66°
Angola
Partly Cloudy
63° wxIcon
Hi: 83° Lo: 60°
Feels Like: 63°
Huntington
Partly Cloudy
66° wxIcon
Hi: 87° Lo: 61°
Feels Like: 66°
Decatur
Partly Cloudy
66° wxIcon
Hi: 87° Lo: 62°
Feels Like: 66°
Van Wert
Partly Cloudy
75° wxIcon
Hi: 87° Lo: 60°
Feels Like: 75°
A weak cold front brings slightly cooler air to the region Tuesday.
WFFT Radar
WFFT Temperatures
WFFT National

Community Events