Extreme cold weather
The strong maritime influence normally prevents very low temperatures in the West Country but surprisingly low minima have been recorded occasionally. In coastal regions the lowest temperatures are found when a strong, cold, easterly wind ousts the normal south-westerlies. Such an occasion was in January 1987, which was probably the coldest day of the 20th century on the coast, with a temperature of -9°C at Newquay. However, an unofficial -18°C was recorded at Porlock in the big freeze-up of 1947. Away from the coast, spells of frosty weather with clear and calm nights have produced records such as -16.1°C at Yeovilton in January 1982. The coldest nights are those on which there is little wind, skies are clear, and there is a covering of snow on the ground; the lowest temperatures occur away from the moderating influence of the sea, on the floors of inland valleys into which the cold air drains. It was under such conditions that the temperature fell to -26.1°C, the lowest ever recorded in England, in Shropshire in January 1982. An unofficial -23°C was recorded at Withypool in the winter of 1940. At the opposite extreme, the highest winter temperatures are apt to occur in the lee of high ground. These high winter temperatures (up to 16°C on rare occasions) occur when a moist south to south-westerly airflow warms up downwind after crossing the top of Exmoor.
Since daily meteorological records began in Britain in the 17th century, there have been a number of severe winters. Records for Exmoor are much more recent and we can only guess that if it was cold in London it was probably worse on Exmoor. The coldest winter of all was probably 1684, when the diarist John Evelyn took a coach to Lambeth along the frozen River Thames. Mid December 1683 saw the 'great frost' start in the UK and Central Europe. the frost was claimed to be the longest on record, and probably was. It kept the Thames frozen a foot deep for 2 months, with a thaw coming in mid February. In Somerset the ground was frozen 4 ft deep and probably more on Exmoor.
Through much of the 17th and 18th Centuries Britain experienced what was known as the 'Little Ice Age'. The Thames froze over most winters in the second half of the 17th century and snow could lie continuously from December to March. There was an exceptionally cold and protracted winter in 1739/40. January in both 1795 and 1814 were colder than January 1740, and the month of February in 1855, 1895 and 1947 was colder than February 1740. What was so remarkable about the 1739/40, however, is that the mean temperatures of both January and February in southern England were below 0°C. The only other known instance of two successive months with mean temperatures below freezing took place in December 1878 and January 1879. Severe winters were commonplace throughout the 18th century and the last time the Thames froze over with a big 'Frost Fair' event was the exceptionally bad winter of 1813-14. It is thought to have been the third worst winter on record after 1683-4 and 1962-3. The frost started in late December. There was a tempoary thaw in January, then the frost returned, possibly more severe than before due to snow cover, and persisted until early February. 1879 had perhaps the coldest summer on record.
January 1881 saw a notorious national freeze-up, when many people were literally frozen to death, some where they stood. The temperature in London was as -18°F. The Thames froze again and even the Baltic froze so that people walked from Denmark to Sweden. At Wellington an ice palace was built. It took 50 men just three days to build and could accommodate 450 people. One room alone was 40X27ft. Admission was charged and a gas supply laid on so that hot drinks could be served.
January 1940 was particularly cold, with skating on Porlock Marsh and thre River Barle and cars driving over the frozen River Exe. 42 degrees of frost (-23°C) was recorded at Withypool and ice brought down power cables and trees. The freeze hit the whole of Europe and was considered to be the coldest spell since 1891. Rivers and coastal waters were frozen.
In mid January 1947, no-one expected the winter to go down in the annals as the snowiest since 1814 and among the coldest on record. After two cold spells that had failed to last - one before Christmas 1946, the other during the first week of January - the weather had turned unseasonably mild: extremely mild in parts, with 14°C being reached. An area of high pressure settled over southern Scandinavia on 20th January and dominated weather over the British Isles for the rest of the month, sending cold air from there to Exmoor, with 42 days and nights of unrelenting frost. The temperature seldom rose more than a degree or two above freezing. The winter began in earnest on the 23rd, when snow fell heavily over Exmoor. The cold, snowy weather continued through February and into March. Any breaks in the cold weather were short-lived. In southern England mean maximum temperatures were everywhere more than 5.5°C below average and, in some places, more than 7°C below average. Mean minimum temperatures were more than 4°C below average in the West Country, and almost 6°C below average in some places. Temperatures would have been lower had it not been cloudy for most of the time. When skies did clear, night-time temperatures plunged.
The winter of 1962/63 was the coldest since 1740. As in 1947, anticyclones to the north and east of the British Isles brought bitterly cold winds from there day after day. Mean maximum temperatures for January 1963 were more than 5°C below average and in some places more than 7°C below average. Mean minimum temperatures over this area were equally far below average. The story was much the same in February. The weather situation began on 23rd December, when high pressure extended all the way from the southern Baltic to Cornwall, bringing cold, easterly winds to Exmoor. The winter of 1947 was snowier but not as cold. In January 1963, there were 25 or more air frosts almost everywhere in southern England. At several stations mean maximum temperatures were below 0°C in January and little higher in February. Mean minimum temperatures were well below freezing almost everywhere in England away from coasts. Even down at Porlock, 30 degrees of frost (-18°C) was recorded. Lakes and rivers froze. Pipes burst, gas mains were severed and reservoirs froze. A highway surveyor said: "My men have been sheeted in ice. They have icicles hanging from their ears and gathering on their eyebrows. Telegraph poles have been iced to double their normal size and electricity cables have measured 6 inches in diameter." Ice formed on harbours such as Watchet, Minehead and Ilfracombe. There were patches of ice on the sea and huge blocks formed on beaches where waves broke and the spray froze. Coastal marine life suffered severely. Winter did not fully relax its grip before early March. In the last few days of February and the first few days of March 1963 sunny weather brought afternoon temperatures of 4 or 5°C, but clear skies allowed temperatures to plummet at night. Frosts were moderate or severe. At last, on 4th March, a mild south-westerly flow of air reached the British Isles, bringing rain. On 6 March, there was no frost and the temperature in London reached 17°C.
1981 saw the coldest December of the 20th century, and also very snowy. It started and ended mild, but there was a severe wintry spell from the 8th to the 27th. Clearing skies, fresh snow, still air, Arctic air, added up to very low temperatures. Temperatures were down to -22°C, only beaten in December by 1995.
Extreme high temperature
England has the longest instrumental record of temperature for anywhere in the world, known as the Central England Temperature series, extending back to 1659. The records confirm the general tendency towards warming. Temperatures over the British Isles have risen by about 0.7°C since 1700 and by about 0.5°C since the start of the 20th century. Correspondingly, extreme high temperatures for Exmoor are mostly recent events and extreme low temperatures largley a thing of the past. However, instances of extreme high temperatures on Exmoor are relatively rare and are associated with hot air brought from mainland Europe on south-easterly winds accompanied by strong sunshine. Records include 35.4°C at Saunton Sands and 34.5°C at Yeovilton, both in August 1990. The highest official UK temperature stands at 38.5°C in Kent in August 2003.
In 1808 there was a memorable heatwave in the middle of July. The spell included "Hot Wednesday": 13 July might have been hotter than any of the record days of the twentieth century. Estimates suggest that it reached 100°F, and might well have reached 40°C (105°F) in places in southern England. There were many heat-related deaths. The extraordinary heatwave concluded with intense thunderstorms. A fireball ripped through Gloucester Cathedral and what was probably the most severe hailstorm to affect the southwest caused great damage. Some hailstones in Somerset were reported to be over a foot long (at 333 mm).
High temperatures coincided with the 'Great Drought' of 1976. In May 1976 a short heat wave led to 29°C being recorded in London. The real heat set in on the 23rd June and for 14 consecutive days the temperature topped 32°C at a number of places in southern England. Many long-standing records were broken. In Dorset and Gloucestershire it exceeded 32°C for seven successive days. This is without parallel anywhere in the British Isles in modern times. At Southampton a reading of 35.6°C on the 28th June ranks as the UK's highest June temperature.
1983 is generally agreed to be the hottest year, with 1976, 1990, 1994 and 1995 are not far behind; yet locally, 1994 was the hottest. The hottest day of the year usually happens in July (about 44% of the time) - and most often between the 10th and the 20th -clearly a good best time to visit Exmoor. Between 1780 and 1830 July was the wettest month of the year. It has since become much drier, so that now it is among the driest months of the year with rainfall averaging 55 mm. Indeed, summer in general has become much drier since 1970.
It is possible that, globally, 2003 was the hottest year ever recorded. The 10 hottest years in the 143-year-old global temperature record have all been since 1990, with the hottest being 2003, 1998, 2002 and 2001. August 2003 was an exceptional month locally, with the maximum temperature in Taunton exceeding 32°C (90°F) on six consecutive days from August 7 -12, peaking at 37.4°C (99.3°F). Such high temperatures have not been seen since July 1976 when the temperature exceeded 32°C on 15 consecutive days between July 1-15. Such high temperatures are normally associated with prolonged periods of drought, when the ground is baked hard and vegetation withers allowing more heat to radiate off in to the air, but this had followed heavy rain.