Question

Why are atlantic hurricanes most likely to form in late summer and early autumn-much later than the time of peak incoming solar radiation?

Answer 1

Just like the warmest time of day is not normally high noon, but mid-late afternoon, the tropical waters which a hurricane derives its energy reach their warmest in the late summer, even though the amount of insolation is decreasing. Most surfaces, especially water, take some time to warm in response to the increase in solar radiation. Also, the upper level winds tend to be more favorable for tropical cyclones in the late summer into fall.
I hope this helps.