Why are there so few marathons in May and June?

It is divided into two aspects: weather and free time.

1, the weather has started to get hot in May and June. Running a marathon in May and June is prone to heatstroke, which will increase the difficulty of the marathon.

2. There are fewer holidays in May and June, less free time for runners and fewer people to sign up for the marathon, so there are fewer marathon events in May and June.