WASHINGTON (AP) — A powerful Hurricane Irma is threatening millions of people in the Caribbean and Florida. Some answers to questions about Irma and hurricanes:

WHERE DO THESE STORMS COME FROM?

Irma is a classic Cape Verde storm, which begin near the islands off the west coast of Africa. Some of the worst hurricanes start as puffs of unstable air and storminess there and chug west, gaining strength over the warm open Atlantic. Another storm, Jose, has followed in Irma's footsteps. Some of those storms fizzle from wind shear or other weather conditions. Still others curve harmlessly north into...