PAGASA acting administrator Vicente Malano said the blue moon is due at 6:43 p.m. on Friday, July 31.
But Malano said a Blue Moon is not necessarily blue, though it can have a bluish tinge in certain atmospheric conditions, such as in volcanic eruptions or in a situation where exceptionally large fires leave particles in the atmosphere.
He said a Blue Moon is the second of two full moons occurring in the same month.
"Since the lunar cycle is 29 days and most months have 30 to 31 days, we eventually find a situation where a full moon occurs at the beginning and the ending of the same month," he said.
This month's first full moon was on July 2. — Joel Locsin/LBG, GMA News