What is the probability the summer solstice will occur on a weekday?

The summer solstice occurs between June 20 and June 21 each year. Since there are 7 days in a week, the probability of the solstice falling on a weekday (Monday through Friday) is approximately 5 out of 7 days. This gives a probability of about 71.4%. However, since the specific day can vary slightly each year, this probability holds true in a general sense over many years.