Bernoulli trial: the risk of a heatwave
Submitted by Camille Démo ✓, Collège Jean-Moulin, Paris · published on September 17, 2026
Model the occurrence of a summer heatwave as a Bernoulli trial and calculate simple probabilities.
Exercise
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.
Explain why a summer can be modelled as a Bernoulli trial. State what counts as a success and give its parameter p.
We observe 3 consecutive summers, assumed to be independent. What is the probability that none of them has a heatwave?
What is the probability that at least one of the 3 summers has a heatwave?
In the 1970s, p was about 0.2. Answer question 3 again with this value and compare.
Show the answer key
Two outcomes: heatwave (success, p = 0.6) or no heatwave (failure, 1 − p = 0.4).
0.43 = 0.064
1 − 0.064 = 0.936
With p = 0.2: 1 − 0.83 = 0.488. The risk over 3 years has almost doubled.
Comments
No comments yet. Tried this exercise in class? Tell other teachers how it went.
Log in with your teacher account to comment.
Log in