May I be the first to wish you a happy summer 2016.
"It's not summer yet" I hear you say. Well that depends on which season calendar you follow - meteorological or astronomical. Today is the first day of summer in the meteorological calendar.
Meteorological Seasons
Meteorological seasons are based on the annual temperature cycle and measure the meteorological state as well as coinciding with the calendar to determine a clear transition between the seasons.
The meteorological seasons consists of splitting the seasons into four periods made up of three months each. These seasons make it easier for meteorological observing and forecasting to compare seasonal and monthly statistics. We generally think of winter as the coldest time of the year and summer as the warmest time of the year, with spring and autumn being the transition seasons, and that is what the meteorological seasons are based on.
By the meteorological calendar (in the northern hemisphere), the seasons are defined as:
Summer: June, July & August
Autumn: September, October & November
Winter: December, January & February
Spring: March, April & May
Astronomical Seasons
The natural rotation of the earth around the sun forms the basis for the astronomical calendar, in which seasons are defined by two solstices and two equinoxes. Traditionally, the astronomical seasons are followed by our weather forecasts on the television, therefore, this is the one we are most familiar with.
Since the astronomical seasons vary in length, the start date of a new season can fall on different days each year. This makes it difficult to compare seasons between different years and resulted in the introduction of the meteorological calendar. The astronomical seasons run approximately three weeks later than those of the meteorological calendar.
By the astronomical calendar, the seasons this year (in the northern hemisphere) start on/around:
Spring: 20 March
Summer: 20 June
Autumn: 22 September
Winter: 21 December
In summary, the astronomical seasons are based on the position of the Earth in relation to the sun, whereas the meteorological seasons are based on the annual temperature cycle.
So get those barbecues ready and have good summers, wherever you are on the globe.