It is relatively rare for the astronomical start of summer (the summer solstice) and Father's Day to fall on the exact same day. [1]The two dates rarely align because they are calculated differently: [1, 2, 3]

• Father's Day is anchored to a weekday rather than a calendar date. It is always celebrated on the third Sunday in June.
• The summer solstice is determined by Earth's tilt and orbit, not our 12-month calendar. It typically shifts between June 20 and June 22. [1, 2, 3]

This means the dates only overlap every several years when the solstice happens to fall on that specific Sunday. According to the Old Farmer's Almanac, such an overlap isn't an annual occurrence