I am bit late on this one, and it won’t come as a big surprise for people further south but spring has sprung, well at least in central England. It happened on the 17th of February and that’s a full 33 days earlier than it normally does on the 21st of March*. I use the number of degree days from the first day of winter to try and put a date to the more than fickle and elusive date for the first day of spring. Using my method it turns out that this first day of spring was the earliest in 31 years, and the fourth earliest since 1772 in the daily CET series. A simple linear trend reveals that the first day of spring occurs three weeks earlier than it did in 1772.
*I’ve fixed the date in my application to the 21st of March fully realising that in 2020 the equinox occurs at 0456 UTC on the 20th of March.