British Weather Extremes
EXTREMES//MAXIMUM TEMPERATURES

Maximum Temperatures

Overview

Wattisham weather stationThe interior of a Stevenson Screen at Wattisham, Suffolk (Credit: Chris Bell)
In 1875 the Royal Meteorological Society organised a network of Climatological Weather Stations, regularly inspected and using verified thermometers. The instruments were exposed in the Standard Stevenson Screen, a procedure also encouraged by the Scottish Meteorological Society and the British Meteorological Office (e.g. for synoptic stations). Summaries of observations from these standard and representative sites were subsequently published in the Meteorological Record of the Royal Meteorological Society, the Journal of the Scottish Meteorological Society, and the Monthly Weather Report of the Meteorological Office. Since 1875 the highest temperature of the year in Britain has been registered as early as 14th May 1965 and as late as 27th September 1895 (for some details, see Journal of Meteorology, 9(87), 69-72). A table of Britain's highest recorded temperatures for each day of the year was originally published in Journal of Meteorology, 9(90), 169-176; a revised list and associated article was published in Weather, 55, pp 298-315. A further revision, plus a full list of UK county extremes (updating the list published in Weather, 48, 282-291), was published as an appendix to the TORRO 40th anniversary book Extreme Weather in 2015, and is available here.

Rhyl weather stationThe Rhyl met enclosure at Bodelwyddan, Denbighshire (Credit: Dan Holley)
The highest mid-winter temperatures are the result of a 'Fohn', where very mild air advected on a south or south-westerly airstream is warmed (by adiabatic compression) on descent from mountain ranges. Outstanding examples include the temperatures of 18.7°C registered in northwest Scotland in December 2019 and 18.3°C recorded in North Wales in January 1958 and January 1971. East Devon, the Welsh borders, North-west and North-east Scotland have also experienced temperatures above 16°C in December or January in similar circumstances.

During early spring the occurrence of very high temperatures still depends on the advection of air from a warm source. This is now most effective across Eastern parts of England when a warm southerly airstream arrives across the relatively narrow eastern English Channel. The latter is also the most favourable situation for high autumn temperatures when sea temperatures are considerably higher but the fading power of the sun ensures that temperatures decline steadily once a supply of warm air has been cut off. North-facing resorts along the East coast of England like Cromer and Whitby (both backed by hills to the South) feature in several of the highest recorded spring and autumn temperatures (e.g. 23.3°C at Cromer on 9 March 1948). This demonstrates how cooling (or, in Spring, chilling!) sea breezes are inhibited by a steady offshore prevailing wind.

Between April and September the direct advection of a very warm air mass is not the only origin of high temperatures; progressively rising temperatures occur during any spells of calm and sunny anticyclonic weather (as in late June 2018) when the highest values are often recorded in Central England, e.g. in the Thames, Severn-Avon and Trent Valleys. The occurrence of numerous extreme Spring, Summer and Autumn maxima in the London area may reflect the "urban effect" but also the fact that the capital is favourably sheltered to the south by the North Downs. While relatively brief incursions of hot air have produced some of the UK’s highest temperatures, including the current record of 38.7°C at Cambridge in July 2019, prolonged heatwaves and the most widespread high maxima are most likely when a very hot air mass stagnates over the country, such as in 1976 and 2003. The record length hot spell of late June to early July 1976 was preceded by a long period of dry, warm weather. The consequent lack of ground moisture resulted in a high proportion of the sun's energy being utilised to heat the air, rather than being used for evaporation.

As during Spring and Autumn very high summer temperatures can be recorded even along the coast when an appreciable offshore gradient wind hinders the development of a sea breeze. The development of these refreshing coastal breezes is also suppressed by the atmosphere stability associated with anticyclones which inhibits the ascent (convection) of hot air inland. In more favourable unstable conditions a `sea breeze' blows inland to replace these ascending currents of warm air. Temperatures above 32°C were recorded at numerous coastal locations during the predominantly anticyclonic heat-waves of June-July 1976 and August 1990. An unusual British `heat-wave' occurred way back on 6th August 1910 when 28°C was registered in the Shetland Isles, while nowhere elsewhere in Britain exceeded 20°C. The extraordinary weather situation responsible is described in Journal of Meteorology, 9(91), 211-213.


Highest recorded temperatures for each month of the year, 1875 to 2020

Month °C °F Location Region Date
January 18.3 65.0 Aber Gwynedd 27 January 1958
18.3 65.0 Aber Gwynedd 10 January 1971
18.3 65.0 Aboyne Aberdeenshire 26 January 2003
18.2 64.8 Llandudno Gwynedd 10 January 1971
February 21.2 70.2 Kew Gardens London 26 February 2019
20.8 69.4 Northolt London 26 February 2019
20.8 69.4 Porthmadog Gwynedd 26 February 2019
20.6 69.1 Teddington London 25 February 2019
20.6 69.1 Trawsgoed Ceredigion 25 February 2019
March 25.6 78.0 Mepal Cambridgeshire 29 March 1968
25.0* 77.0* Wakefield West Yorkshire 29 March 1929
25.0* 77.0* Wakefield West Yorkshire 29 March 1965
25.0 77.0 Cromer Norfolk 29 March 1968
25.0 77.0 Santon Downham Norfolk 29 March 1968
24.9 76.8 East Dereham Norfolk 29 March 1968
April 29.4 85.0 Camden Square London 16 April 1949
28.9 84.0 Cambridge Cambridgeshire 20 April 1893
28.9 84.0 Kensington London 16 April 1949
28.9 84.0 Wealdstone Greenwich 16 April 1949
May 32.8 91.0 Camden Square London 22 May 1922
32.8 91.0 Horsham West Sussex 29 May 1944
32.8 91.0 Tunbridge Wells Kent 29 May 1944
32.8 91.0 Camden Square London 29 May 1944
32.8 91.0 Regents Park London 29 May 1944
June 35.6 96.1 Southampton, Mayflower Park Hampshire 28 June 1976
35.6 96.1 Camden Square London 29 June 1957
35.5 95.9 Southampton, Mayflower Park Hampshire 27 June 1976
35.4 95.7 North Heath West Sussex 26 June 1976
35.4 95.7 East Dereham Norfolk 26 June 1976
July 38.7 101.7 Cambridge Botanic Garden Cambridgeshire 25 July 2019
38.1 100.6 Cambridge NIAB Cambridgeshire 25 July 2019
37.8 100.0 Heathrow London 31 July 2020
August 38.5* 101.3* Faversham Kent 10 August 2003
38.1 100.6 Kew Gardens London 10 August 2003
37.9 100.2 Heathrow London 10 August 2003
37.9 100.2 Aldenham Hertfordshire 10 August 2003
September 35.6 96.0 Bawtry South Yorkshire 2 September 1906
35.0 95.0 New Malden London 1 September 1906
35.0 95.0 Maidenhead Berkshire 1 September 1906
35.0 95.0 Colly Weston Northamptonshire 1 September 1906
35.0 95.0 Barnet London 2 September 1906
34.8 94.6 Epsom Surrey 2 September 1906
34.8 94.6 Old Southgate London 2 September 1906
34.6 94.2 Raunds Northamptonshire 8 September 1911
October 29.9 85.8 Gravesend Kent 1 October 2011
29.4 84.9 March Cambridgeshire 1 October 1985
29.4 84.9 Charlwood Surrey 1 October 2011
29.3 84.7 Santon Downham Suffolk 2 October 2011
29.3 84.7 Coningsby Lincolnshire 2 October 2011
28.9 84.0 Whitby North Yorkshire 1 October 1908
28.9 84.0 Kensington Palace London 5 October 1921
28.9 84.0 Kensington Palace London 6 October 1921
28.9 84.0 St James' Park London 6 October 1921
28.9 84.0 Hampstead London 6 October 1921
November 22.4 72.3 Trawsgoed Ceredigion 1 November 2015
22.3 72.1 Trawsgoed Ceredigion 2 November 2015
21.7 71.0 Prestatyn Clwyd 4 November 1946
21.1 71.0 Cambridge Cambridgeshire 5 November 1938
21.1 71.0 Chelmsford Essex 5 November 1938
21.1 71.0 Mildenhall Suffolk 5 November 1938
21.1 71.0 Clacton Essex 5 November 1938
21.1 71.0 Tottenham London 5 November 1938
21.1 71.0 Halstead Essex 5 November 1938
December 18.7 65.7 Achfary Sutherland 29 December 2019
18.3 65.0 Achnashellach Highland 2 December 1948
18.0 64.4 Aber Gwynedd 18 December 1972
17.8 64.0 Aber Gwynedd 17 December 1972
17.7 63.9 Cape Wrath Highland 18 December 1972
17.7 63.9 Penkridge Staffordshire 11 December 1994

Note: Values qualified by an * are either (a) from rather sheltered sites or (b) more than 2°C above adjacent stations.