Rainy Day Demisting: A Complete Guide to Clear Windows

Fogged-up windows on a rainy day are frustrating — and the harder you work, the worse it can get. Here's how to tell where the fog is, and the right way to clear it in seconds.

Every rainy or humid day, drivers face the same problem: car windows that fog up just when you need to see clearly. If you're wondering how to stop windows from fogging up, or how to demist a windscreen fast, this guide is for you. Many people try everything at once — only to make the fog worse. The root cause is usually simple: they haven't worked out which side of the glass the moisture is on, so they're using the wrong fix. Let's sort it out.

Is the fog inside or outside?

The first step in any demisting routine is knowing where the fog is. Run a quick test with your finger:

• You can wipe a visible streak on the inside of the glass — the fog is inside the cabin.

• Your finger leaves no mark — the moisture is condensing on the outside of the glass.

Why windows fog up

Inside fog happens when warm, humid cabin air — from breathing, sweat or wet items you've brought in — meets a cold windscreen and condenses into fine droplets on the glass. It's the classic foggy windscreen scenario on a wet morning. Outside fog happens when the air outside is humid, and the glass is cold. The higher the humidity and the lower the glass temperature, the worse it gets.

Clearing fog from the inside

Here's the correct sequence when the fog is inside:

• Step 1 — switch on the air-conditioning. Tap the A/C button to start cooling. This is the fastest way to demist a windscreen from the inside. This is the crucial step: the air-con's core job here is dehumidifying, not cooling. It condenses moisture out of the air and removes it, fixing the problem at the source.

• Step 2 — set the controls. Keep the temperature at 26°C or below — cold air is what removes humidity effectively. Switch the mode to the windscreen airflow, and turn the fan up high for the fastest result. Also switch to fresh air intake: recirculating cabin air just moves moisture around in a loop.

• Step 3 — use one-touch demist. Tap the one-touch demist icon on the centre screen (the fan-shaped symbol), or use the voice assistant to start front demisting. It takes around 10 seconds to clear the windscreen. You can also use AUTO mode, which sets everything correctly for you.

Two extra helpers: crack a window open by about one or two fingers' width to let dry outside air in. In heavy rain, don't open it too wide — you'll wet the interior.

Important Note: With XPENG XHP 3.0 Smarter Anti-Fog Strategy, the auto humidity control in spring/fall can help you prevent window fogging, and the anti-fog sensors will intelligently assist in mitigating fogging risks.

Common mistakes that make it worse

• Using warm air only. Heat makes the cabin comfortable, but warm air doesn't remove moisture — the fog can get thicker.

• Setting the temperature too high. Above 26°C, the dehumidifying effect drops sharply and fog lingers. Around 2°C below the outside temperature is the sweet spot.

• Using fresh air intake without the A/C. Ventilation alone just swaps air around; without the air-con, humidity stays high and keeps cycling inside the cabin.

Clearing fog from the outside

Outside fog needs the opposite approach. It's a common windscreen fogging problem that heat can't fix:

• Use the wipers to clear the windscreen.

• Never switch on the windscreen demist or "blow windscreen" mode. Those functions blow warm air onto the glass, which widens the temperature gap and makes outside fog worse.

• Check the vent aim. Make sure the vents aren't pointed at the windscreen, and adjust or close them if they are.

• For the rear window, switch on the rear demister — it shares a button with the heated mirrors. The heating element quickly evaporates moisture on the outside of the rear glass.

• For the side windows, a quick trick works: roll the window down once and back up, letting the glass edge wipe the droplets away. Side windows often lack a dedicated demist vent, so raise the airflow and open a window briefly to move humid air out.

• In extreme conditions — big temperature differences and heavy fog — clear the outside first, then raise the cabin temperature and open a window to ventilate. As the inside and outside temperatures come closer together, the outside fog clears on its own. Be patient for a minute or two.

• If outside fog keeps coming back no matter what you try, have the glass seals and the air-conditioning system checked at your XPENG service centre.

The bottom line

Demisting is about knowing which side of the glass is wet. Inside fog needs cold, dry air from the air-con; outside fog needs wipers, not heat. Get that right, and you'll clear any rainy-day fog in seconds.