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Page last updated at 17:28 GMT, Friday, 10 September 2010 18:28 UK
Devon's maritime climate explained
David Braine
By David Braine
BBC South West weather presenter

Saunton Sands
Water has a much higher heat capacity than soil and rock

The South West has a maritime climate but what does this actually mean?

We have the longest coastline of any region in England and as a result we are never too far away from the sea and its influence.

In contrast to continental climates, maritime climates experience generally cool summers and mild winters, with a much smaller annual temperature range.

This is because water has a much higher heat capacity than soil and rock.

Seawater takes a long time to warm up in summer, but once heated it retains its energy long after the surrounding land has cooled down, helping to moderate the climate.

Maritime climates generally are fairly humid, accompanied by considerable amounts of precipitation, since the main moisture source is not very far away.

The South West experiences a typically maritime climate, with prevailing south-westerly winds from the Atlantic Ocean.

The maritime air masses that influence this part of the world are particularly mild on account of the warming influence of the Gulf Stream.

The annual average temperature range in the UK is only about 10°C.

Lightning in Plymouth
In July and August thunderstorms with lightning can occur

Although the west coasts of Canada and Alaska experience maritime climates, the absence of an equally significant warm Pacific current in the mid latitudes means that these regions are generally colder in winter, with more precipitation falling as snow.

Typical winter weather in Devon and Cornwall is clouds and rain with the occasional sunny spell.

The moors may have snow on them for many weeks in winter, but falls on the lower ground on only a few days a year, and is generally not a feature of the climate.

Temperatures hover around a January average of 5ºC. Overnight temperatures often drop below freezing point, and ice and frosts are common.

Each winter there are a few weeks when the temperature does not rise above freezing point and we can get frozen ground for a few days but it rarely lasts.

Typically, summers are warm with some sunshine but can often be cloudy with rain.

Light rain occasionally occurs on days like these, but summer rain is usually restricted to a very wet days.

In July and August, the conditions can become very humid and thunderstorms can occur with lightning.

The average July temperature is around 15-17ºC, although temperatures in excess of 30ºC are not unheard of.

The prevailing winds are from the southwest, moist air from the direction of the Gulf Stream which brings temperate conditions.

Occasionally there is a cold wind from the north, bringing very cold weather from the Arctic, characterised by icy winds, snow and frost and the last two winters have been like this.

On the whole the maritime climate of the South West is beneficial to us and wildlife, the abundance of water and the lack of extreme weather make it one of the most temperate places to live in the world, and arguably the best.




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