Log on to insuremytrip.com, quotetravelinsurance.com, and tripinsurancestore.com to compare plans; what they cost, cover, and pay out varies widely. But after reviewing a policy, there's one important question left: When are you not covered?

You bought insurance after a weather warning was issued

"Preexisting conditions" aren't covered by health insurance, and events deemed "foreseeable" aren't covered by travel insurance. To safeguard against the weather, your insurance must be purchased before the National Weather Service (nws.noaa.gov) issues a storm warning.

The weather's not bad enough

Insurers will only pay when travel gets delayed or canceled. If the airlines and the cruise ships are operating, you can either go on the vacation or lose your money.

Your cruise itinerary changes

When a port is expecting a rough storm, cruise lines often substitute a different port where the weather is more promising. If the cruise takes place--even if the new ports are second-rate--the insurance company doesn't owe you a dime. Plead with the cruise line instead; it might give out vouchers for future cruises.

You're not delayed long enough

Benefits don't kick in the moment your flight is delayed. Instead, there's a waiting period--typically 5 to 12 hours, depending on the policy--before you can book a hotel for the night and expect to get reimbursed.

The delays have made you want to cancel

The initial flight on your seven-day trip to St. Thomas is postponed overnight, and you have to stay at an airport hotel (covered under your policy, thank goodness). The next day, flights are still delayed. You want to scrap the trip, but you can't--not if you hope to get reimbursed. With some policies, more than half of your vacation has to be delayed before you can cancel and be covered.

The hotel is ruined, but the airlines are flying

A hurricane hits Jamaica two weeks before your trip, ripping the roof off your hotel. If flights are running on your departure date, insurance might not do you any good. Even if your hotel is completely destroyed, most policies don't have to pay, as long as you can still get there. One exception is from Travel Guard, which words its policy more broadly than others and ponies up if the destination is ruined.