Based on the CET temperature series since 1900.

Average Summers with an average temperature =15.0°C 16.0°C
Total 51 years or 1 in 2 years

YEAR , JUNE , JULY , AUGT , SUMM
1900 , 14.7 , 17.7 , 15.1 , 15.83
1901 , 13.9 , 18.0 , 15.6 , 15.83
1904 , 13.3 , 17.1 , 15.1 , 15.17
1905 , 14.7 , 17.2 , 14.7 , 15.53
1906 , 14.3 , 15.8 , 16.7 , 15.60
1914 , 14.5 , 15.8 , 16.1 , 15.47
1917 , 15.2 , 16.1 , 15.3 , 15.53
1923 , 12.5 , 17.5 , 15.2 , 15.07
1925 , 15.0 , 16.8 , 15.4 , 15.73
1926 , 13.6 , 17.1 , 16.2 , 15.63
1930 , 15.3 , 15.2 , 15.7 , 15.40
1932 , 14.1 , 16.1 , 17.1 , 15.77
1936 , 14.7 , 15.3 , 16.1 , 15.37
1937 , 14.1 , 16.1 , 16.9 , 15.70
1938 , 14.4 , 15.2 , 16.3 , 15.30
1939 , 14.2 , 15.5 , 16.4 , 15.37
1940 , 16.4 , 15.1 , 15.6 , 15.70
1941 , 15.1 , 17.3 , 14.7 , 15.70
1942 , 14.4 , 15.5 , 16.6 , 15.50
1943 , 14.4 , 16.4 , 16.1 , 15.63
1944 , 13.5 , 16.5 , 17.0 , 15.67
1945 , 14.6 , 16.7 , 15.9 , 15.73
1950 , 16.2 , 15.9 , 15.6 , 15.90
1951 , 14.0 , 16.3 , 14.8 , 15.03
1952 , 14.4 , 16.8 , 15.8 , 15.67
1953 , 14.4 , 15.5 , 16.2 , 15.37
1957 , 15.2 , 16.3 , 15.4 , 15.63
1958 , 14.1 , 15.9 , 15.8 , 15.27
1960 , 16.1 , 15.1 , 15.0 , 15.40
1961 , 14.4 , 15.2 , 15.4 , 15.00
1964 , 13.8 , 16.1 , 15.5 , 15.13
1966 , 15.4 , 15.0 , 14.7 , 15.03
1967 , 14.0 , 16.7 , 15.7 , 15.47
1968 , 14.8 , 15.0 , 15.4 , 15.07
1969 , 13.9 , 16.8 , 16.4 , 15.70
1970 , 16.4 , 15.2 , 16.0 , 15.87
1973 , 14.8 , 15.6 , 16.5 , 15.63
1979 , 13.9 , 16.2 , 14.9 , 15.00
1982 , 15.5 , 16.5 , 15.7 , 15.90
1991 , 12.1 , 17.3 , 17.1 , 15.50
1992 , 15.7 , 16.2 , 15.3 , 15.73
1996 , 14.4 , 16.5 , 16.5 , 15.80
1998 , 14.2 , 15.5 , 15.9 , 15.20
1999 , 13.9 , 17.7 , 16.1 , 15.90
2000 , 15.1 , 15.5 , 16.6 , 15.73
2002 , 14.4 , 16.0 , 17.0 , 15.80
2007 , 15.1 , 15.2 , 15.4 , 15.23
2008 , 13.9 , 16.2 , 16.2 , 15.43
2009 , 14.8 , 16.1 , 16.6 , 15.83
2010 , 15.2 , 17.1 , 15.3 , 15.87
2012 , 13.5 , 15.5 , 16.6 , 15.20