The planet Mercury reaches greatest eastern elongation of 23.6 degrees from the Sun. This is the best time to view Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the western sky just after sunset.
In the northern hemisphere, this marks the first day of summer and is the day with most hours of light in the year — when the Sun is farthest north. In the southern hemisphere, this is your winter solstice, marking the shortest day of the year.