On Monday, May 9, Mercury will slowly make its way across the Sun’s disk. The transit of Mercury is a rare event, as we've discussed before, with only about a dozen occurring every century. This one will be visible in full from the easternmost side of the Americas, western Europe, and north-west Africa. It lasts several hours, so people from Bangladesh to California will be able to catch at least part of this astronomical event.
The transit will start at about 7 a.m. EDT (noon BST) and finish at about 3 p.m. EDT (8 p.m. BST). The precise time can be found by using a planetary app, and it depends on where you are on Earth. Alternatively, Eclipse Wise has a list of transit times covering 100 U.S. and Canadian cities.
Global Visibility of the Transit of Mercury on May 09, 2016. F. Espenak, Eclipse Wise
To observe this phenomenon you’ll need a telescope with the correct solar filter. Mercury will cover about 0.004 percent of the Sun, so it will be very difficult to see without a telescope and it should not be attempted without protection. If you don’t have a telescope, the Royal Astronomical Society has compiled a list of public events related to the transit of Mercury.
Note, you should never look at the Sun directly with the naked eye. You wouldn't be able to spot the transit, anyway.
If the weather is not good or there are no events in your area, you can still follow the event on the Slooh website, where they will have a live broadcast using their telescope in the Canary Islands to follow our Solar System's smallest and innermost planet flying across the Sun.