From observations over the period 1951−2009 eight heat waves were extracted for the Paris Basin, i.e. a mean frequency of about 1 in 7 years (a heat wave being defined as at least one day with daily minimum 18°C and maximum 34°C, minimum duration of 3 days with relatively high temperatures).

In addition, for the periods 1960−1989, 2020−2049 and 2070−2099, the numbers of heat waves were projected (using the aforementioned definition of a heat wave) based on (1) several (regional and global) climate models and the A1B emission scenario, and (2) one regional climate model and 3 emission scenarios (A2, A1B, B1).

For the period 1960−1989 on average one heat wave in 10 years was calculated, for 2020−2049 1 heat wave every 2 years was projected, rising to at least 1, and up to 2, heat waves per year on average over 2070−2099. Heat wave duration also increased in time, with mean durations varying between 6 and 12 days over 2070−2099, and exceptional durations reaching 5 to 9 weeks.

Source: Lemonsu et al., 2014. Climate Research 61: 75–91.

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