On July 2, Super Typhoon Maria formed as a tropical depression at 2040 hours. Barely eight hours later, on July 3, 0410 hours Maria became a tropical storm near Guam. For the next 28 hours, Maria slowly strengthened as a tropical storm.
On July 5, 0840, it was like an explosion occurred, for in the space of 30 minutes, Maria spiked from a 53 knot tropical storm to a 72 knot typhoon, equal in strength to a category one hurricane.
Maria only remained at a category one equivalent hurricane strength for nine hours, when her pressure dropped and she blew through a category two to a category three equivalent hurricane in 2 hours, from July 5 1740 to 1950. Typhoon Maria only remained at a category three strength for five hours, when at July 6, 0040 hours, she became a super typhoon with 115 knot sustained winds.
Maria was not done strengthening. She accelerated to 135 knot sustained winds, a category 5 super typhoon by July 6, 0840 hours, in just eight hours.
So from July 5, 0910 a category 1 to July 6, 0910 a category 5!
Tropical Cyclone Scales: https://en.wikipedia.org/wiki/Tropical_cyclone_scales#Western_Pacific
Super Typhoon Maria Intensification:
Super Typhoon commentary and updates: http://cimss.ssec.wisc.edu/goes/blog/archives/28799