You don't need 4 season tents for camping in the summer. Even if it rains a lot, sleeping pads and good planning should keep most things from getting too wet. The important thing is not to camp at the bottom of a hill, to make sure the rain fly is secure, and to use natural cover.
But a four-season tent is nice to have in extreme weather, and if you have the money to buy one, it can really make your camping experience better.
The main difference between a 4 season tent and a regular tent is that a 4 season tent is tighter and has thicker walls on the outside. When it is completely closed, there is no way for the weather to get in.
Also, 4 season tents are usually more stable, so they can stand up to very heavy storms if they need to. But this doesn't mean you can't use four-season tents when the weather is nice. Many 4 season tents have an outer fly that can be unzipped so you can stay cool in the summer and stay warm when it's almost as cold as the North Pole in the winter.
You will find, though, that a 4 season tent is more specialised the more extreme the conditions for which it was made. For example, you might not want to take some true mountaineering 4-season tents camping on a warm summer night.
The ventilation panels are small, so if you use them to go camping in the summer, it will be stuffy and hot at night. They are also made of heavier, stronger materials, which makes them harder to carry on a normal camping trip.
And, of course, good four-season tents can be very expensive, sometimes costing more than $500. Compare this to a summer tent for one or two people that you could get at a camping store.
I bought mine for $30, and even though it doesn't keep me very warm, it works fine in the summer when I use it with a good sleeping bag.
Before you go out and spend a lot of money on expensive mountaineering gear and 4-season tents you won't need, you should think about what you will be doing. You must make sure that your tools can do what they are meant to do.
