The season of Summer starts on 6th May and ends on the 5th August.
The English language and the body of knowledge known as science, clash in ridiculous chaos when it comes to something as mundane as defining Summer.
What is summer? My pocket Oxford says it is the "Second or Hot SEASON". It says that a SEASON is "one of the divisions of the year associated with a type of weather and astronomically begins in the 4th week of December, March, June or September". Look around on Google and again there is an astronomical definition that Summer begins with the Summer Solstice and ends on the Autumn Equinox.
This is science? This is language? It's ridiculous enough to permit an 11-year old illiterate child from one of Britain's failing schools, to go and stand on a University Campus and start laughing at the academics.
Should it not be obvious that Summer is the one quarter of the year whence the maximum possible (i.e. without cloud cover) amount of daylight reaches the Earth's surface ? Then there is a consistent definition of summer on every latitude of the Earth, except on the infinitesimally exact line of the Equator.
This would mean that the 91 and something days of summer begins about 45 and a half days before the Summer Solstice. In other words, Summer starts around the 6th May, and ends around the 5th August, with the exact time and date varying up to +/-12 hours from GMT depending on your timezone.
To define Summer as the 91 and something warmest days in the year makes the summer season dates completely variable according to latitude and local climate. In fact, the closer you approach the Equator, the more variable the results of these dates. Not to mention that even in Britain, the variation between microclimates on isolatitudinal lines could cause the "start of the warmest season" to vary as widely as 3 weeks.
To use the astronomical definition of summer, which says that the summer season starts at the summer solstice, completely ignores any consideration of trying to ascertain which are the most Solar - Energized days of the year. The sun's main usefulness is as a source of Energy to the Earth. To define Summer as beginning on the Summer Solstice, would require that Spring is defined as beginning on the Spring Equinox. This would mean that Spring and Summer, as seasons would have equal levels of High Total Solar Energy reaching the Earth. This would also mean that Winter and Autumn would have equal levels of Low Total Solar Energy reaching the Earth. From this point of view, the year is divided into only two portions.
From a language point of view, this defeats the usefulness of defining a Season. The purpose of a classification of seasons is to divide the year into more meaningful discrete equal segments. Four distinct Seasons are more meaningful than two.
See what I mean about the mess of the English Language and Basic Science? I wonder who is in charge of the English Language, these days. Maybe not Oxford University, maybe Google?