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Posted at 10:45 AM ET, 07/23/2012

London 2012 Summer Olympics weather: Recent rain concerns give way to sunny, drier conditions


Workers and the Olympic Rings are reflected in the rain outside the basketball arena at Olympic Park, Friday, July 20, 2012, in London. (Charlie Riedel - AP)
Following weeks of heavy rain and a dismal summer across Britain, the weather forecast for the opening ceremony of the London 2012 Olympics is showing signs of improvement. Warmth and sunshine are finally making an appearance in the UK as temperatures in the south of England climb past 77 degrees (25ºC) for the first time this month.

The latest five-day forecast from the Met Office calls for “very warm and fine conditions” across the southern UK, with temperatures in London possibly reaching 86 degrees (30ºC) or higher by midweek.

Yet for the opening ceremonies on July 27 there is a bit more uncertainty as an area of low pressure in the north Atlantic approaches Scotland later this week. The good news is that temperatures in London and southern England should stay mild with highs in at least the low-70s (20-23ºC) through the start of the weekend. The downside is that rain chances also increase and temperatures drop a few degrees as the Olympic Games get underway.

While the weather during the Olympic games still remains a question mark, the Met Office has cautioned that “a lengthy spell of hot, sunny weather looks unlikely.”

What is typical summer weather in England?

England’s recent bout of heavy rain and cooler than normal conditions certainly reinforces the stereotype of lousy British weather. Yet summer in the southern United Kingdom can be quite pleasant with stretches of sunny days in the mid-70s or higher (24ºC+).

The city of London has an oceanic climate and sees its warmest annual temperatures from late-July through early August – neatly coinciding with the 2012 games. Average daily high temperatures are around 74 degrees (23ºC) with nighttime lows averaging 57 degrees (14ºC) downtown.


Comparison of daily average and recorded high/low temperatures at London (Heathrow) since June 1, 2012. Dotted lines indicate five-day forecast. (wunderground.com, adapted by CWG)

UK’s summer of 2012 wet so far

Unfortunately, such picturesque summer weather has not been the case in 2012 – a year in which winter drought conditions suddenly gave way to excessive rainfall during spring. The Met Office reports that April-June was the UK’s wettest three-month period on record.

June alone recorded more than twice its normal monthly precipitation (145.3 mm, or 5.7”), making it the UK’s wettest such month since records began in 1910. July started on the same note, with some areas receiving over 250 percent of normal monthly rainfall within one week.

The cause of the damp weather is the jet stream, which has been tracking farther south than usual for this time of year. Limited sunshine has brought cooler than average temperatures to most of the UK, including London, seen in the graph above.

The myth that it always rains in England

Despite common belief that it always rains in England, this idea refers more to the frequency rather than the quantity of rainfall. London actually averages less annual precipitation than many U.S. cities on the East Coast and in the Midwest, such as New York, Chicago, and Washington, D.C. For example, London’s average annual precipitation of 23.3” is well below Washington’s 39.7 inches.


Average precipitation in London and Washington, D.C. by month in inches. (CWG)

In the United States, many locations east of the Mississippi River receive abundant rainfall due to both summer thunderstorms and the abundance of tropical moisture from the Gulf of Mexico. Hurricane and tropical storm systems can also bring these locations inches of rain within just a few days.

In the UK, on the other hand, prevailing westerly winds bring a steady stream of clouds and rain off the Atlantic, but these weather systems usually contain less atmospheric moisture due to Britain’s more northern latitude. Note from the graph above that even during its wettest month (November), London averages slightly less precipitation than Washington does during its driest month (February).

How to prepare for British weather?

Whether you’re off to England for the Olympics or a vacation, be sure to take an umbrella and light jacket along. Even if Britain does see some warmer, sunnier weather in the weeks ahead, it’s probably not to last long.

Useful links

Weather Guide for the 2012 Summer Olympic Games (Met Office)
The UK’s wet summer, the jet stream, and climate change (Met Office)
Why won’t it stop raining? (The Telegraph)

By  |  10:45 AM ET, 07/23/2012

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