As any head of state can attest, not all dates of birth are equally convenient. June is pretty much the ideal month for holding birthday celebrations. Not yet as hot as July or August, it is decidedly warmer and sunnier than May, with less a chance of rain showers than in September. The weather in June is quite simply inviting. It is a pleasure to meet on a well-manicured lawn, in the pleasant shadow of a historic palace, and toast to His Majesty's most excellent health.
In matters of state, the actual date of birth is far less important than the convenience of June. The current reigning sovereign of the United Kingdom, HM King Charles III, first saw the light of day on 14 November 1948. It was a month not really known for its light or pleasant weather. Thus, it was natural to observe the tradition of the House of Windsor, and move the official celebrations to a month with more reliable sunshine.
The reason is simple. In reality, royal birthdays are only tangentially connected with the life of a monarch. It is not a private occasion but a decidedly public one. The King is respected but not worshipped. The King's Birthday is a celebration of a constitutional monarchy, an occasion for all his subjects, across all his nations, to have a good time.
Contemporary kingship shares only a few traits with its medieval or even ancient forms. Yes, there is pomp and circumstance and in the United Kingdom, a lavish coronation in the same hallowed halls of Westminster Abbey. But even the most fearless forbears would shudder if faced with the ordeals of contemporary monarchs and their immediate families. Each and every year, the tallies are indeed awe-inspiring. The Royal Family carries out about 2,000 official engagements annually and entertains about 70,000 people at lunches, dinners, receptions, and garden parties. They receive, and answer, about 100,000 letters.
"In reality, royal birthdays are only tangentially connected with the life of a monarch. It is not a private occasion but a decidedly public one."
Jure Stojan, partner and director of R&D at the Institute for Strategic Solutions (ISR)
For each of these guests and correspondents, even the fleetest contact with a member of the Royal Family is a matter of lifelong memories. For the King and the Royal princes and princesses, it is a full-time job, scripted to detailed agendas, and undertaken with impeccable manners, etiquette, and a friendly smile - even when they do not feel like smiling. Their role is to create positive impressions on an almost industrial scale. All their lives, they have trained in how to make even the shortest interactions pleasurable.
So, having an official birthday in June is only a continuation of the same logic. The predictably nicer weather makes it easier to create beautiful memories.