when will blue moon appear

The next Blue Moon will appear on May 31, 2026, at 08:45 GMT. This will be a calendrical Blue Moon. The next seasonal Blue Moon is expected on May 20, 2027. Blue Moons occur about every 2.5 to 3 years and are defined either as the second full moon in a calendar month (calendrical Blue Moon) or the third full moon in an astronomical season that has four full moons (seasonal Blue Moon).