How an Atlantic hurricane forms

I got this great explanation from my awesome brother who is a forcaster with the national weather service.

1. Warm sea-surface temps of >=80 deg F.
2. The second factor is a result of the spinning motion of the earth, called Coriolis force. Basically, the rotation of the earth could cause a circulation to form, which could eventually lead to a hurricane. The circulation may start off as an elongated area of low pressure, technically known as a trough. The equator separates the direction of spin. That's why hurricanes north of the equator spin counter-clockwise, while south of the equator they spin clockwise.
3. Another important factor is the vertical wind shear. Basically, this means that the wind must be roughly the same speed and direction all the way up into the atmosphere.

All these factors are optimized in late summer.