Expert comment: King set for dry coronation, records suggest

Well-wishers lining the streets for the coronation of King Charles III are set for a pleasant day with plenty of sunshine and without rain, if historical weather trends are followed.  

The landmark event is just under a fortnight away and millions of people are expected to watch the King make his way to Westminster Abbey on Saturday, 6 May.  

But the state of the weather may affect just how many people turn out to catch a glimpse of history.  

Dr Stephen Burt, from the University of Reading’s Department of Meteorology, has looked back more than a century at what the weather has been doing on May 6 in years gone by. 

The figures below are based on the University's records which go back to 1908 for temperatures and rainfall, to 1956 for sunshine, and taking the 30-year averages 1991-2020. 

Dr Burt said: “The mean daily maximum temperature on 6 May averages 16.9 °C, a little cooler than the May average as it's early in the month. Temperatures on the date have ranged from just 9.2 °C (in 1932) to 25.5 °C (in 1995). The chance of 20 °C is about 1 in 4 (7 times in 30 years). 

“The daily average for sunshine on 6 May is 6.8 hours, a little higher than May's average of 6.4 hours. In 2020, 14 hours of sunshine was recorded - making this the sunniest 6 May on our records. There was zero sunshine on 6 May, 1962. On 6 May, 11 days in 30 years had 9 hours or more sunshine, six of those 12 hours or more. So the chances of 9 hours of sunshine are better than 1 in 3. 

“On 6 May in 30 years, 7 days had 25% or less cloud cover, and 8 days were completely cloudy. 

“The average rainfall for 6 May just 0.8 mm - the May average is 1.4 mm/day. Exactly half of the 30 years remained completely dry on 6 May, and only 9 years received 0.2 mm or more. Only once has the date received more than 10 mm, and that was back in 1925 (10.7 mm). Only twice in the past 30 years has 5 mm fallen on this date. No snow or sleet has fallen on 6 May, and only two years in 30 recorded thunderstorms.

“Last year, 6 May saw a maximum temperature of 21.0 °C, a minimum of 7.7 °C, 0.8 mm of rainfall and 7.2 hours of sunshine. 

“Based purely on climatology, we might expect a dry and fairly sunny day that is a little on the cool side. It is important to be clear that this is not a forecast as such – that will have to wait for a little closer to the date itself as weather forecast models have little reliability that far ahead. We should have a fairly good feel for how the day will shape up from around 4-5 days beforehand.”