After a few mornings of showers and storms, clouds are set to clear on Tuesday when Mars will pass close to Earth. This will be the closest approach since 2003. All of these factors mean that not all close encounters are equal. In 2003, Mars made its closest approach to Earth in nearly 60,000 years! It won't be that close again until the year 2287.
Now you're thinking how close is close for the 31st? It will be 35.8 million miles away. However, it will appear much bigger and brighter to the naked eye. Even better through a telescope. By mid-August, Mars will become fainter as Mars and Earth travel farther away from each other in their orbits around the Sun.
The close encounter happens about every 26 months. However, the Red Planet comes close enough for exceptional viewing only once or twice every 15 or 17 years.
The next close approach will be in October of 2020 when it will be 38.6 million miles away from us.