Hottest day of each year from 1900

1900 35.1 Cambridge 20 July

1901 33.3 Bawtry (South Yorks.), Colly Weston (Northants.) 19 July, Newton Rigg (Cumbria) 20 July

1902 31.9 Hereford 28 June

1903 31.1 Wryde (Cambridgeshire) 10 July

1904 32.2 Margate 4 August

1905 30.0 Bawtry (South Yorks.) 14 July

1906 35.6 Bawtry (South Yorks.) 1 September

1907 30.0 Lairg 16 July

1908 32.8 Dumfries 2 July

1909 33.3 Epsom 15 August

1910 28.9 Maidenhead 20 June

1911 36.7 Raunds, Canterbury 9 August

1912 32.8 Tottenham 12 July

1913 29.4 New Malden (London) 16 June

1914 32.2 Woking, New Malden, Wisley (Surrey) 1 July

1915 32.2 Cromer, Norwich 8 June

1916 30.0 Woking 30 July, Salisbury 31 July

1917 33.9 Reading, Little Massingham (Norfolk) 17 June

1918 33.9 Canterbury 22 August

1919 32.2 Raunds 11 September

1920 27.8 Raunds 17 June

1921 34.4 Woking, Halstead (Essex) 11 July

1922 32.8 Camden Square 22 May

1923 35.6 Camden Square 13 July

1924 32.2 Camden Square 12 July

1925 33.3 Hunstanton 22 July

1926 32.2 Camden Square 19 September

1927 29.4 Camden Square 16 June

1928 32.8 Camden Square, Newport (IOW) 15 July

1929 32.2 Camden Square, Margate 31 August; Newport (IOW) 5 September

1930 34.4 Camden Square 29 August

1931 28.3 Bromley 14 June

1932 36.1 London (several sites, inc. Camden), Tottenham, Halstead 19 August

1933 34.4 Margate, Cambridge 27 July

1934 33.3 Attenborough (Notts.) 11 July

1935 33.3 Attenborough (Notts.) 13 July

1936 31.7 Camden Square 20, 21 June

1937 33.3 Canterbury, Tunbridge Wells 7 August

1938 30.6 Camden Square, Reading 1 August

1939 32.2 Camden Square 7 June

1940 32.8 Cranwell (Lincs.) 9 June

1941 34.3 Camden Square 22 June

1942 33.9 Sprowston (Norfolk) 27 August

1943 33.9 Worcester, Croydon 31 July

1944 32.8 Tunbridge Wells, Horsham, London 29 May; Long Sutton (Hants.) 30 May

1945 32.2 Norwich, Whitstable 15 July

1946 30.6 London 2 July, Finningley 12 July, Greenwich and Maldon 24 July

1947 34.4 Waddingtn (Lincs.), London 3 June

1948 35.0 Milford (Surrey) 28 July

1949 33.3 Worcester 12 July

1950 33.3 Camden Square 6 June

1951 30.0 Southend 28 July

1952 33.9 Jersey 1 July; 33.3 Camden Square, Heathrow, Southampton 1 July

1953 33.9 Camden Square 12 August

1954 30.6 Camden Square 1 September

1955 32.8 Jersey 21 August (32.2C Chivenor, Devon, on 23 August)

1956 30.0 Camden Square 26 July

1957 35.6 Camden Square 29 June

1958 29.4 Paisley 4, 5 July; Leicester 8 July

1959 34.4 Cromer, Boxworth, and St James's Park 5 July

1960 30.6 Wyton (Cambs.) 18 June

1961 33.9 Regents Park, Camden Square, Gillingham 1 July

1962 27.8 Writtle (Essex) 3 September

1963 28.9 Littlehampton 22 July; Ceinws (Powys.) 29 July; Wisley, Gordon Castle (Gramp.) 30 July

1964 32.8 Cromer 26 August

1965 28.9 Kensington Palace 14 May

1966 28.9 Southampton 9 June; Perth, Crossmyloof (Strathclyde) 21 July; Camden Square (20 August)

1967 30.2 Watnall (Notts.) 17 July

1968 33.3 Camden Square 1 July

1969 32.8 Letchworth (Herts.) 16 July

1970 32.2 Aldenham (Herts.), Stratford-upon-Avon 7 July

1971 30.3 Rugby 11 July

1972 29.4 Perth 20 July

1973 32.1 Southampton 14 August

1974 28.0 Southampton 15 June

1975 34.2 Heathrow, Stanstead Abbotts (Herts.) 8 August

1976 35.9 Cheltenham 3 July

1977 30.0 Paisley, Glenlee (D. & G.) 7 July; Onich (Highland) 11 July

1978 28.8 Poolewe (Highland) 4 June

1979 30.4 Benson (Ox.) 27 July

1980 29.4 Cors Fochno (Dyfed) 4 June

1981 29.5 Kew 5 August

1982 30.7 Morley St. Botolph (Norf.) 3 August

1983 33.0 East Bergholt (Suffolk) 15 July, Hampton 16 July

1984 31.9 St Louis (Jersey) 20 Aug (31.7 Heathrow on 8 July)

1985 30.1 St Louis (Jersey) 13 July (29.8 Heathrow 25 July)

1986 32.0 Rustington (W. Sussex) 28 June

1987 30.2 Liphook (Hants.) 21 Aug

1988 30.2 Cheltenham (Glos.) 7 Aug

1989 34.4 Mickleham (Surr.) 22 July

1990 37.1 Cheltenham 3 Aug

1991 32.1 Cromer (Norf.) 11 July

1992 30.3 Malvern 29 June

1993 29.7 East Bergholt (Suff.) 4 July

1994 33.4 Morley St Botolph (Norfolk) 12 July

1995 35.2 Boxworth (Cambs.) 1 Aug

1996 33.2 Rickmansworth 22 July

1997 33.1 Wellesbourne (Warks.) 10 August

1998 32.2 Gravesend 10 August

1999 32.7 Heathrow 1 August, Honington (East Anglia) 2 August

2000 32.6 Coltishall (Norfolk) 19 June

2001 32.2 Northolt (London) 26 June

2002 32.6 Northolt (London) 29 July

2003 38.5 Brogdale, near Faversham (Kent) 10 August; with some debate, and 38.1C at Kew is more reliable

2004 31.5 Northolt (London) 8 August

2005 32.6 Heathrow 19 June

2006 36.5 Wisley (Surrey) 19 July

2007 30.1 Terrington St. Clement, Wisbech (Norfolk) 5 August

2008 30.2 Cambridge 28 July

2009 31.8 Wisley (Surrey) 30 June

2010 31.7 Gravesend 9 July

2011 33.1 Gravesend 27 June

2012 32.4 Cavendish (Suffolk) 18 August

2013 34.1 Heathrow 1 August

2014 32.3 Swancombe Marsh (Kent) 18 July

2015 36.7 Heathrow 1 July

2016 35.2 St Hellier, Jersey 19 July (34.4 Gravesend 13 September)

2017 34.5 Heathrow 21 June

2018 35.6 Felsham (Suffolk) 27 July

2019 38.7 Cambridge Botannical Gardens 25 July

Some points about hot days

An annual maximum of less than 90F has happened just under 50% of the time since 1900 (90F is 32.2C). Since 1900,

34C or more seen 24 years, in (10 times 34-35:1921, 1930, 1933, 1941, 1947, 1959, 1975, 1989, 2013, 2017 plus the 14 years below.

35C or more has been seen in just 14 years from 1900 on (1906, 1911, 1923, 1932, 1948, 1957, 1976, 1990, 1995, 2003, 2006, 2015, 2018, 2019),

36C or more has been seen in 7 years  (1911, 1932, 1990, 2003, 2006, 2015, 2019)

37C or more twice (1990 and 2003),

38C or more twice (2003 and 2019).

The summer of 1976 was exceptional in containing 5 consecutive days above 35C. The lowest annual maximum is 27.8C, recorded in 1920 (Raunds) and 1962 (Writtle, Essex).

The earliest date on which 90F (32.2C) has been reached was on the 22 May 1922; the latest date was 19 September 1926.

The hottest summer days occur when a very hot air mass (drawn up from the Continent on a southerly or southeaserly airflow) stagnates, with very little wind. Temperatures are likely to be higher after a lengthy spell of dry weather (e.g. 1911, 1976, 1990) because more of the sun's heat is used on heating the air rather than evaporating moisture from the ground. If there is wind, sheltered spots are favoured. This is one reason why London fares so well; in addition to any urban heating, it is sheltered from southerly winds by the North Downs. The anticyclone stops the hot air mixing vertically. Obviously the higher the angle of the sun the better (you can't hope for too much on Midwinter's Day!). It helps if the soil is dry, so that energy isn't "wasted" evaporating soil water.

Hottest day for each extended summer month and hottest days since 1900

May               32.8 (1922, London; 1944, London)

June               35.6 (1976, Southampton), 34.5C (2017, Heathrow)

July               38.7 (2019, Cambridge Botannical Gardens), 36.7 (2015, Heathrow),  36.0 (Greenwich and Epsom, 1911), 35.9 (1976 at Cheltenham).

August          38.5 (2003, Faversham), 37.1 (1990, Cheltenham, 3rd)

September     35.6 (1906, Bawtry), 34.6 (1911, Raunds), 34.4 (2016, Gravesend),

The history of the hottest day in Britain

2019               38.7C reported at Cambridge Botanical Gardens, 25 July

2003               38.5C reported at Faversham, 10 August (disputed, 38.1 accepted)

1990               37.1C at Cheltenham, 3 August

1911               36.7C at Raunds and Canterbury, 9 August

1868               Before 1911 things are less clear. 38.1C (100.5F) was reported as being recorded at                Tonbridge on the 22nd, although the screening was nonstandard and this temperature is now recognised as being far too high. The temperature was more likely actually around 36.5C (97-98F).