The other day I was listening to a BBC forecast and heard John Hammond say that hot days like Tuesday (19th of July 2016) were not as unusual as you might think (or words to that effect). That got me thinking about just how rare or common exceptional days were in the Central England Temperature [CET] series, so I delved into the statistics to find out…
As far as I can make out there have been around 95 days which had an anomaly of +10.0°C or greater since 1880 ((extreme high maximum events) in the CET series. That may sound a lot, but don’t forget that’s over a period of 135 years, or almost 50,000 days, so that makes the average interval between exceptional warm days at once every 17 months or so, and don’t forget this type of event is not just limited to summer months, they can and do occur in any month between March and October.
Below are a couple of tables. The upper table is of totals that are grouped by decade, and the highlighted column is of warm days with anomalies >=10°C. The lower table is a list of all extreme warm events from 1970 to 2016, and as you can see first and latest entry is Tuesday’s event (19 July 2016) with a provisional CET of 31.5°C or +11.35°C above the long-term average for that particular day. Tuesday’s event wasn’t the first ten degree event of 2016, the first one was occurred in a warm spell on the 8th of May, but I bet the majority of people will hardly remember that one. Last year there was only one ten degree event which of course is the one that occurred on the 1st of July 2015. Before that you have to go back almost four years to find the previous ten degree plus event which was also fairly notable as being the warmest October day on record if memory serves.
This application is still not finished, but already it’s thrown up some interesting statistical results. The 1941-1950 period has the record number of extreme high maximum +10 degree events in any decade which surprised me, and what about the period between 1976 and 1990, almost 14 years without a ten degree anomaly event. Also the table lists no ten degree high mean events, but around 37 extreme low mean events. Perhaps I’ve screwed up somewhere, I would have expected there to have been an equal number of hot and cold extreme mean events – but not none and 37!