A fogged windshield always seems to happen when you are in a hurry. Understanding why it forms makes it easy to clear fast and keep clear.
Why glass fogs up
Fog forms when moist cabin air meets glass that is a different temperature. In winter, warm damp air condenses on cold glass inside. In summer, humid outside air condenses on cool glass when the air conditioning is on.
Clearing fog in cold weather
Turn on the defrost setting, set the temperature warm, switch off recirculate so drier outside air comes in, and turn on the air conditioning if your car allows it while heating. The air conditioning removes moisture even when the air is warm. Crack a window slightly to speed it up.
Clearing fog in warm weather
This fog is on the outside of the glass, so the wipers clear it. Nudge the temperature slightly warmer so the glass is closer to the outside air temperature.
Stop it coming back
Keep the inside of your windshield clean, since dirt gives moisture something to cling to. A glass treatment and a small moisture absorber in the cabin both help in damp climates.
Frequently asked questions
Should I use recirculate to defog?
No. Recirculate keeps humid air inside and makes interior fog worse. Use fresh air.
Why does my windshield fog only in the morning?
Cool overnight glass plus damp cabin air. Running the defrost with air conditioning clears it quickly.
For glass care products, see our car accessory guides.
