Weather: United Kingdom
You're never far from the ocean when you're in the United Kingdom. That fact tells you a lot – though hardly everything – about British weather. The climate here feels undeniably moist, yet the rain is by no means constant. Most of England gets measurable moisture not quite every other day, often amounting to little more than a good round of drizzle. Many of these rains come and go quickly: some parts of central England average little more than an hour a day of precipitation. Atlantic lows tends to make their way across Ireland and Scotland, which keeps those regions considerably wetter and breezier than England. Wales and the Lake District also see a good deal more rain than southeast England. Persistent rain over a few days may cause localized river flooding; on the other hand, it's possible to go a week or longer without any rain at all.
Since Britain's rains tend to come in briefer spells during summer than in winter, the sun pokes out much more regularly then. The brightest spots are often along the coastlines, as clouds build just inland during the day and form offshore at night. Many parts of England get about a dozen thunderstorms each year, mostly on summer evenings and nights. Though mild by US standards, a few of these produce hail and even a weak tornado. Once or twice each summer (more often in some years), high pressure parks over the UK, producing a few days of heat that may feel intense for visitors. No location in the UK had ever reached the 100°F mark until the astounding heat wave of 2003: on 10 August of that year, it hit 38.5°C (101.3°F) in Faversham, Kent, and both Heathrow Airport and the Royal Botanic Gardens in London topped 100°F. Scotland tends to be a few degrees cooler than England – a trend especially noticeable in summer, when 20°C/68°F constitutes a warm day for a town in the Highlands. The Shetlands and Outer Hebrides are even more vulnerable to gusty, chilly conditions in summer, not to mention hurricane-force winds and seemingly interminable rain and cloud in winter.
Although sunny spells do occur even as the days grow darker, the overcasts of late autumn and early winter can seem relentless – and sometimes they are. London once suffered an entire month (December 1890) without a single hour of sunshine. As winter sets in, gales frequently buffet the coasts, especially toward the north and west. While mid-winter is seldom bitterly cold, it's consistently chilly. The UK's warmest winter temperatures actually occur along the northeastern sides of Scottish mountains when Atlantic southwesterlies approach. As they flow over the peaks and descend, they can warm to 16°C/60°F or greater.
Winters vary greatly in the extent of snow and below-freezing cold snaps they produce. Snow almost never falls on the western fringes of Cornwall and Pembroke, while the Pennines and the uplands of Wales average more than 40 snow days a year and parts of the Grampians over 70. Snow may persist near the highest peaks well beyond winter (Britain's last continuous snow patch, near Ben MacDhui, melted in September 1933, although snow persists in some summers). Prolonged spells of bright, crisp weather become more likely in February and especially March, as the strong Atlantic flow weakens a bit. A few cold air masses may still slide down from the Arctic or push across from the Continent, bringing late frost. In general, rainfall amounts slacken across the UK in the spring. Temperatures are rapidly nearing their summer peaks in May, which gets as much sun as July in many spots (except for the northeast coasts, where clouds are still rolling in from the North Sea).