Office for Climate Education

Bernoulli trial: the risk of a heatwave

Première40 minAnglais

Proposé par Camille Démo, Collège Jean-Moulin, Paris · publié le 17 septembre 2026

Model the occurrence of a summer heatwave as a Bernoulli trial and calculate simple probabilities.

Énoncé

According to Météo-France records, the probability that a given summer brings at least one heatwave to a city in the south of France is estimated at 0.6 over the recent period.

  1. Explain why a summer can be modelled as a Bernoulli trial. State what counts as a success and give its parameter p.

  2. We observe 3 consecutive summers, assumed to be independent. What is the probability that none of them has a heatwave?

  3. What is the probability that at least one of the 3 summers has a heatwave?

  4. In the 1970s, p was about 0.2. Answer question 3 again with this value and compare.

Voir le corrigé
  1. Two outcomes: heatwave (success, p = 0.6) or no heatwave (failure, 1 − p = 0.4).

  2. 0.43 = 0.064

  3. 1 − 0.064 = 0.936

  4. With p = 0.2: 1 − 0.83 = 0.488. The risk over 3 years has almost doubled.

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