Artist's impression of the Hitchin to Great Offley hailstorm (Chris Chatfield).

Several hailstorms have reached H7 in Britain, but only one H8 has been recorded. On May 15, 1697, a H8 hailstorm tracked from Hitchin to Great Offley (Hertfordshire) - although this makes a track length of only 5 km, the true hail swathe must have been much longer. No equivalent data is currently available for the continent.

Heaviest Hailstone
The heaviest hailstone recorded in Britain fell from the H7 storm which tracked 150 km from West Wittering (West Sussex) to Maldon (Essex) on September 5, 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).

No equivalent data is currently available for the continent.

Hailstorms in Great Britain (General)
For the recent period from 1981 to 2000 potentially damaging hail (TORRO intensity of H1 or more) was reported on between 6 and 28 days each year with an average annual frequency of 15 days in Great Britain .

Analysis of TORRO's database of more than 800 hailstorms which reached an intensity of H3 or more reveals that the early summer experiences the highest proportion of such storms, with more than half (52%) occurring in June or July. Around three-quarters of all these hailstorms (77%) occurred between May and August, with June experiencing the peak monthly frequency (29%).

The area most frequently affected by hail damage extends from Lancashire, Greater Manchester, and Merseyside, southeastwards to the counties in and around the Thames Valley (Berkshire, Bedfordshire, Buckinghamshire, Hertfordshire, Oxfordshire) and Greater London, and to parts of East Anglia (Cambridgeshire, Essex and Suffolk).

For further details see 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