If the sunshine is so strong outside, you'd better wear the sunglasses to help your eyes from the uv rays and other bad lights. If you don't wear the sunglasses, your eyes will hard to open under the strong lights. What's worse, the eyes will get burned if you are at outside for a long time under the strong sun lights.
Well, there are actually many benefits to wear sunglasses when you go outsides. Of course, they can shield your eyes. As we know that no matter it is sunny or cloudy, people are exposed to ultraviolet (UV) rays from the sun. And these kinds of rays are invisible and also very harm to our health. So you should wear sunglasses to protect eyes from the harmful rays. Many people know that there is need to protect their skin from the sun, but not everybody knows that it is equally critical to protect eyes. But some researches have shown that exposure to bright sunlight may increase the risk of developing conditions, such as cataracts, age-related macular degeneration and growths on the eye, including cancer. So you should wear sunglasses to decrease the risk of getting those kinds of diseases.
Well, it seems that you are not very familiar with sunglasses. To be honest, by wearing sunglasses when we go out in a sunny day, we could better protect our eyes from some harmful lights. On the other hand, without sunglasses, our eyes will suffer from those lights and could not even do our work or travel. Of course it is bad for our eyes without sunglasses in a hot day. Anway, a pair of polarized sunglasses could be your perfect companion outside.