If you want to travel to The United Kingdom you should dispose of reliable information about UK weather and especially about UK rainfall. Short periods of intense rainfall can cause flash flooding, longer periods of widespread heavy rain can cause rivers to overflow and storm surges can cause coastal flooding.
Rainfall in England varies widely.

The Lake District is the wettest part, with average annual totals exceeding 2,000 mm (this is comparable with that in the western Highlands of Scotland). The Pennines and the moors of south-west England are almost as wet. However, all of East Anglia, much of the Midlands, eastern and north-eastern England, and parts of the south-east receive less than 700 mm a year.

Typically, it rains on about one day in three in England, perhaps somewhat more often in winter, though long, dry spells occur in most years. Near the south coast there is an appreciable summer minimum and winter maximum of UK rainfall, with totals in July barely half those in January; western, northern and eastern coasts are more likely to see the driest month in spring and the wettest in late autumn. Inland, parts of the Midlands experience a summer rainfall maximum, which is a reflection of the higher frequency of thunderstorms in the more central and south-eastern parts of England. For example, at London and Birmingham, thunder occurs on an average of 15 days a year, but in the west and north-west the frequency declines to around eight days per year.

Of the four constituent countries of the Wales, Wales has the highest average UK rainfall. It boasts the wettest inhabited place in the UK, eight of the wettest towns, and the wettest city. the highest average annual totals being recorded in the mountainous areas of Snowdonia and the Brecon Beacons, where the yearly fall is comparable with that in the English Lake District or the western Highlands of Scotland. In the east, close to the border with England, annual totals are similar to those over much of the English Midlands. Snowdonia is the wettest part of Wales with average annual totals exceeding 3,000 mm, but coastal areas and the east receive less than 1,000 mm a year. Throughout Wales, the months from October to January are significantly wetter than those between February and September, unlike places in south-east Scotland or in the English Midlands where July and August are often the wettest months of the year. This is a reflection of the relatively low frequency of thunderstorms in Wales, compared with that in England. For example, at Cardiff, thunder occurs on an average of 11 days a year, compared with 15 to 20 at many places in England. In the west and north-west the frequency declines to around eight days per year.

There is a general misconception that the whole of Scotland experiences high UK rainfall. In fact, rainfall in Scotland varies widely, with a distribution closely related to the topography, ranging from over 3,000 mm per year in the western Highlands (comparable with rainfall over the mountains of the English Lake District and Snowdonia in Wales) to under 800 mm per year near the east coast (comparable with the Midlands of England). (Note that rainfall also includes snow, which is melted and measured as rainfall.)

The seasonal variation of rainfall in Northern Ireland is not large, but throughout the Province the wettest months are between August and January, unlike places in south-east Scotland or in the English Midlands, where July and August are often the wettest months of the year. This is partly a reflection of the relatively low frequency of thunderstorms in Northern Ireland, compared with that in England. For example, at Armagh, thunder occurs on an average of less than four days a year, compared with 15 to 20 at many places in England. Only in a few locations, mainly away from the coasts, does the frequency of thunder exceed five days a year.

So, to have a vacation of a lifetime check the forecast on the website of UK Meteorological Office. The Meteorological Office operates an extensive network of weather stations, reporting in real time. It also coordinates the making of climate observations by a large number of voluntary climate and UK rainfall stations, whose cooperation is gratefully acknowledged.