The first rule when the weather is bad is to slow down. In fog use low beams; you’ll get less glare than with high beams. If necessary, drive at a crawl so that you can stop within the range of visibility. Another car’s taillights may shine through fog, but you can’t assume that they will.
If you decide to stop, don’t do so suddenly; cars behind may not be able to respond quickly. Signal and pull off the road completely so that cars behind won’t mistake you for a moving vehicle and plow into you. Put on your hazard flashers.
In heavy rain at speeds above 35 mph, beware of hydroplaning (tires riding on a cushion of water, causing loss of steering control). If it occurs, take your foot off the accelerator to slow the car and hold the steering wheel as straight as possible. Don’t hit the brakes.
Crawl through deep puddles; otherwise water may splash the ignition wires, causing the engine to stall. Water may also affect the brakes. Drive slowly and apply the brakes several times to revive their stopping power.
On dirt roads or salted snowy roads dirt may coat the headlights, reducing night visibility. Pull off the road periodically to wipe the lenses.
In heavy snow, you need snow tires. Don’t rely on all-season tires; they are designed for light snow. Consider premium snow tires with treads that perform better than ordinary ones at low temperatures.
Carry a shovel and sand or traction mats. Stuck? A gentle acceleration, then a release, may pull you out. Don’t spin your wheels, and don’t rock more than a few times or you’ll damage an automatic transmission.
On ice, make no sudden moves. If you skid, turn the steering wheel in the direction the car’s rear is sliding. Be especially cautious at temperatures around 32F; ice is most slippery then.