During which months does Lake Ontario experience the highest percentage of thunderstorms?

The correct answer encompasses the months of May to September because this period typically coincides with the warmest months of the year when conditions are most favorable for thunderstorms. During these months, increasing temperatures and humidity lead to heightened atmospheric instability, which are crucial factors in the development of thunderstorms.

In the spring and summer months, particularly from late spring into early fall, the combination of warm air and moisture creates the environment necessary for storm development. Thunderstorms tend to occur more frequently during this time, as warm, moist air rises and cools, leading to cloud formation and precipitation.

While other options include months that may still experience some thunderstorms, they are usually less prevalent in the cooler months of January to March or during early spring. Therefore, the highest percentage of thunderstorms is best represented by the months of May to September, making this the most accurate choice.