The safest way to drive when it rains is to reduce your speed. When you drive at lower speed, you will have better control over your car. In heavy rain the windshield wipers can sometimes struggle in removing the water quickly enough for you to be able to have a clear sight of the road. In heavy rain, the water can often flood the street with water, making driving more challenging.
The condition of your tires will also determine how fast you can drive. Some tires are more suitable to drive in rainy conditions than others and this depends on the design of the treads. The tread design helps the tire to channel water out of the way, while remaining in contact with the road surface. The higher the speed you drive at, the less time the tire has to push the water to the sides and you will eventually reach the state of aquaplaning, where the tire looses contact with the road surface. This is a dangerous state to be in, as you have lost all control over your car at this point. The loss of traction of the tires to push the car forward is also lost, which will cause the car to slow down and eventually gain contact again with the road surface.
It is not only the design of the treads that have an impact, but also the depth. The lower depth, the smaller the volume is within the tread as it touches the ground. It is this volume of which the tire can push water aside; so the lower the volume is the less water can be removed from the surface. So a worn out tire has almost no possibility to push any water aside, thus you will experience aquaplaning much earlier than with a tire with good tread depth. This is one of the reasons why it is very important to keep track of your tread depth to make sure that it is still in good condition. It is also illegal to drive with tires that are below a certain tread depth. If you have summer tires on your car, the level is 2/32”.
So make sure that you keep your tires in good condition and above that level. Also make sure that you reduce your speed when it rains, so that you can drive safely.