British Extremes

Artist's impression of the Wellesbourne hailstorm
(Credit: Chris Chatfield)
Earliest severe (≥H3) hailstorm
The earliest known severe hailstorm in Britain occurred at
Wellesbourne in Warwickshire in
May 1141 and
was at least H3 in intensity on the TORRO Hail Scale. However, there are believed to have been one or more fatalities caused by
hail - which would infer very large stones and hence a much higher intensity rating.
No equivalent data is currently available for the continent.
Longest-track hailstorm
On
22 September 1935, an H6 hailstorm tracked 335 km from the west-south-west from
Newport (Gwent) to
Mundesley (Norfolk). It is likely that the true length was longer still, as the storm probably tracked along the Bristol Channel for some distance before reaching Newport, as well as continuing over the North Sea after Mundesley.
No equivalent data is currently available for the continent.

Artist's impression of the Hitchin to Great Offley hailstorm (Credit: Chris Chatfield)
Most intense hailstorm
Several hailstorms have reached H7 in Britain, but only one H8 has been recorded.
On
15 May 15 1697, an H8 hailstorm tracked from
Hitchin north-eastwards to
Potton (Bedfordshire), a storm swathe at least 25 km long.
At Offley, near Hitchin in Hertfordshire, the hailstones were measured at 343 mm circumference with some anecdotal reports indicating 445 mm.
These correspond to measurements of about 110 and 140 mm diameter, respectively, and the pieces of ice were described as 'some oval, some round, some flat'.
The ground was torn up, and great oak trees were split. Tiles and windows of houses were all shattered to pieces. At least one human fatality was attributed to the hail, a young shepherd.
No equivalent data is currently available for the continent.
Heaviest hailstone
The heaviest hailstone officially recorded in Britain fell from the H7 storm which tracked 150 km from
West Wittering (West Sussex) to
Maldon (Essex) on
5 September 1958 - the stone, which fell on
Horsham (Sussex), weighed 190 g. However, descriptions from older accounts which do not usually quote weights clearly indicate that significantly heavier stones have fallen in Britain (even when suspected exaggeration is taken in to account). In the great
Somerset hailstorm of
15 July 1808, many were reported as weighing over 220 g.
No equivalent data is currently available for the continent.
Webb, J. D. C, Elsom, D. M, and Reynolds, D. J (2001) Climatology of severe hailstorms in Great Britain, Atmospheric Research 56, pp 291-308
Webb, J.D.C., Elsom, D.M., Meaden, G.T. (2009) Severe hailstorms in Britain and Ireland, a climatological survey and hazard assessment. Atmospheric Research, 93, 587–616.
Webb, J.D.C., Elsom, D.M. Severe hailstorms in the United Kingdom and Ireland: a climatological survey with recent and historical case studies. In: Extreme Weather. Forty years of the Tornado and Storm Research Organisation (TORRO), 1st Edition. Wiley-Blackwell and John Wiley and Sons: Chichester, UK (Chapter 9).