Cornwall’s weather is one of the many things that inspires people to take a holiday here, instead of jetting away to more exotic foreign climes. OK, we also have history, culture, arguably the best beaches and seaside activities, and a narrow and uncluttered geography that makes it easy to get around and to make the best of whatever the day throws at us. But ask most people what’s so special about the county, and they’ll probably mention the weather, or something that relies irrevocably upon it.
Kernow’s summer sunshine is very well known, and many people visit the Duchy between May and September, when temperatures are regularly above 20°C/68°F, sometimes reaching 25°C/77°F and have even soared above 30°C/86°F in recent years.
The county has what is technically known as a temperate Oceanic climate, (with the possible exception of the far west tip and the Isles Of Scilly, see below), and hence the climate is exceptionally mild. It’s interesting to think that the westernmost point in mainland England is Land’s End, and The Lizard is also the most southerly point. The influence of this south-westerly location, closest to the European mainland, and more importantly the warm sea currents flowing either side of it, means that spring can arrive weeks earlier than in other parts of the UK. Daffodils, in particular, often flower around Christmas in the area, and this is an indication of how much warmer winters are here, when compared to other parts of England. As a result of this favourable year-round weather, people often choose to visit the county out of season, when it’s considerably less busy. Autumn is an excellent time to come, and although the evenings are beginning to feel cooler, the weather is generally warm, making beaches and coastal walks enjoyable. Stunning sunsets, though hardly rare here, are especially common at this time of the year in Cornwall. At times the consistent sunshine can last for several weeks, with hardly any rain at all.
Warm sea, you say?
It is a weather fact commonly misunderstood – many people think of the sea as cold, and it may be if you’re venturing out in Speedos in the winter – but the sea is on average warmer than the land. Sea water slowly absorbs any heat that the sun radiates down to it, whereas the ground warms up only at the surface and then cools down again almost as soon as the sun goes in. So, ignoring any effects you might feel of the sun on your back or the ground being warm underfoot, one can understand that the sea is actually like a blanket helping to keep the land warm when the sun goes down. In July 2014 the sea temperature around Cornwall had already reached 20ºC with two months at least of warming weather still to go. With the average air temperature at 16º (day and night averaged), it’s easy to see how the ocean stops the land mass getting too cold.
The climate of Cornwall is, then, unusually mild and on top of that blessed with nearly 17% more hours of sunshine per year than the UK average. For the stats geeks, that’s over 1540 hours of sunshine per annum. The highest average, 7.6 hours of sunshine per day, occurs in July. Winters are among the warmest in the country because of the extreme southerly location and the moderating effects of the ocean currents (the land mass is narrow, so everywhere is close to the sea, and the Gulf Stream/North Atlantic Drift has more impact on Cornwall’s coasts than other regions). On paper, the bare figures show that Cornish summer temperatures are also slightly moderated by the influence of the sea breezes, and hence can be slightly cooler than some other parts of the southern UK, but because of the unique micro-climate of the south-west peninsula, the hot days feel hotter than anyone in Britain would imagine possible.
Indeed, the Scilly Isles and the far western tip of the Cornish mainland are regarded by some experts as the only sub-tropical climate in the UK. This sub-tropical meteorology is one reason for the great diversity of plant life unseen in most other British outdoor locations. Palm trees and other exotic flora like fig trees and tropical flowers are commonplace in Cornwall, while being almost unheard of in parts of the nation. And by the same virtue, there are many exceptional botanical gardens in the county – The Lost Gardens of Heligan, and Pencarrow, to name but two (the Eden Project is another great resource but it’s cheated a little bit with enclosed biodomes). The exotic-looking monkey puzzle tree (Araucaria araucana), actually native to Chile and Argentina, reputedly got its modern name from a comment once made at Cornwall’s Pencarrow gardens; “It would puzzle a monkey to climb that tree!”
Incidentally, and while on the subject of trees, the winds in Cornwall blow so much of the time from the south-west (this is what is called the “prevailing” wind) that many of the trees exhibit a profound lean, or even a strangely “windblown” look to their foliage even on a calm day, so much of their time have they spent in the face of this south-westerly breeze.
Many places stands out from the already illustrious Cornish climate, by being sheltered from the prevailing south-westerly winds, yet with the slope of the land facing the sun for the entire day at most times of year. Newquay, Padstow, Port Isaac on the north coast, and Charlestown, Polruan, Polperro on the south are all great examples of places where the water frontage enjoys a particularly excellent microclimate. Add to this the advantage of warm rocks and white sand, and it is sometimes hard to believe we aren’t in the Mediterranean, especially when basking in the sun overlooking turquoise seas – the water in Cornwall is exceptionally clean.
One can expect rain every month of the year in the UK, but Cornwall gets most of its rainfall in the months from October to March, and much of this falls on the higher ground inland. The rainfall averages for the county are quite misleading in this respect, as the west facing coastal regions are not usually mired in wet weather.
Mizzle is a term often heard in the south-west. It refers to a sort of mixture of mist and fine rain or drizzle which seems to float rather than fall while retaining the ability to drench those who walk about in it. It’s also rather impervious to light, and can make a bad day in Cornwall feel as though the sun never quite properly came up. A day like this is sometimes called a dimpsey by rural folk. Those who know Cornwall, but are not au fait or comfortable with the local term for the phenomenon, sometimes refer to it as Cornish mist. Not to be mistaken for ordinary mist. Or for valley mist, most common in spring and autumn; cold but dry, and burns off in the heat of the sun.
Snow and frost
Snow and frost are not completely unheard of in Kernow, but they are less common than in other parts of Britain. While many living Cornish people can remember one or two winters when snow covered the ground right down to the coasts for a few days, these are few and far between. It’s very unusual ever to have more than a dusting of snow, even on the high ground. While there may be overnight frosts in Cornwall, especially in moorland areas, there are normally not more than a few each year, a fact most pleasing to the gardeners of the region!
While extreme temperatures in Cornwall are statistically quite rare, the nature of the topography, the geographical position protruding into the Atlantic and facing both the prevailing winds and the natural direction of travel of most weather systems, means that Cornwall experiences a fair amount of changeable or even stormy weather. Visitors do come to the county to enjoy the bracing weather and spectacular seas as well as the calm and sunshine. As a side note, we should mention that big surf is not caused by storms in Cornwall. The weather that makes the waves happens over the other side of the Atlantic, anywhere from Newfoundland down to the Caribbean, and while the waves themselves reach our Cornish beaches, the storms that created them have usually fizzled out somewhere over the ocean.
Despite being well known for wind and waves, the last time that Cornwall experienced a tsunami was in 1755, from the earthquake epicentred in Lisbon, Portugal. Not really a big worry, then. Localised flooding does occur in some places in the wet months, especially October and March, but the nature of the fishing ports and villages is such that this rarely causes inconvenience, let alone danger or loss of life.