Fog is fairly common, particularly in spring and early summer, and the occasional tropical storm or hurricane can threaten the region, especially in late summer and early autumn. Due to its situation along the North Atlantic, the city often receives sea breezes, especially in the late spring, when water temperatures are still quite cold and temperatures at the coast can be more than 20 °F (11 °C) colder than a few miles inland, sometimes dropping by that amount near midday. Thunderstorms occur from May to September, that are occasionally severe with large hail, damaging winds and heavy downpours. Although downtown Boston has never been struck by a violent tornado, the city itself has experienced many tornado warnings. Damaging storms are more common to areas north, west, and northwest of the city. Boston has a relatively sunny climate for a coastal city at its latitude, averaging over 2,600 hours of sunshine per annum.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): What months do thunderstorms occur in Boston?
May to September