British Weather Extremes: Hailstorm

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. 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.

Artist's impression of the Wellesbourne hailstorm
Artist's impression of the Wellesbourne hailstorm.
(Chris Chatfield)

Longest-Track Hailstorm

On September 22, 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.

Most Intense Hailstorm

Artist's impression of the Hitchen to Great Offley hailstorm
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, 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 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). 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.

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 for 1930–2009 identified 620 hailstorms that reached a significant, damaging intensity of H2 or more.
The early summer experiences the highest proportion of such storms, with 50% occurring in June (27%) and July (23%). A separate analysis of hailstorms of intensity H5 or more (specifically H4–H5 or more and usually involving hail ≥50mm diameter) which have occurred in Great Britain from 1800 to 2009 indicated that the peak monthly incidence of these more severe storms is slightly later than for all hailstorms of intensity H2 or more, with July accounting for 41% of these events followed by June (21%); 93% occurred between May and August.
The full database of H5+ storms can be accessed in Appendix A.

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). The geographical distribution of storms of H5 intensity or more indicates a conspicuous maximum occurrence towards the south-east Midlands and central East Anglia.

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
Webb, J.D.C., Elsom, D.M., Meaden, G.T. (2009) Severe hailstorms in Britain and Ireland, a climatological survey and hazard assessment. Atmos. Res., 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).