From summer droughts to mild winters and snowy snaps in the spring, the seasons of the UK seem to be transforming. Our expert seasonal weather guide is researching into the cause of that transformation and the potential effect for nature.
When does spring start?
At this time of year, we usually receive a collective question, as regular as clockwork: “When does the spring come into officially start?”. And then we always give the same answer: “It all depends”.
Meteorological definition of seasons
For some weather experts, records are very important, so for consistency, climate statisticians regard March 1st as the official beginning of spring, with the entire months of March, April, and May as obviously defining the season. It’s brief and plain and enables us to reach a benchmark for the data, whatever the whims of weather from year to year.
The three months from June consist of summer. Autumn slips during September, October, and November, with the last three months completing winter. But can we track our seasons into neat, equal chunks when the meteorological ‘goalposts’ are continuously slipping from day to day and from year to year?
Astronomical definition of seasons
You perhaps prefer the astronomical definition and look at the sun as your guide. About three weeks after the climatological start of spring, the equinox traces the trice the direct sun passes the equator and returns into the northern hemisphere after six months down south.
The sun itself is not moving; it’s the earth tilt when it orbits the sun that forms this passage of light and heat around the world.
How does phenology signal the seasons?
There has been a third measure, much more liquid and moveable, based on phenology. The tokens are all around us in nature, providing each of the seasons its hallmark. In the winter, lower temperatures, snow as well as frost and cold rain enables animals to hibernate and makes plants more dormant to save energy.
In the spring, the natural world re-awakens and sets off its race for development. In the summer, when verdant energy reaches a climax, so crops come to fruition. Then as light and temperatures wane so the pace of life puts on the brakes and nature gets ready for winter again.