As soon as the flight information board shows your flight as "canceled," start dialing your airline's customer service number. Some airports also have banks of phones that are open for passengers to use for re-booking. It doesn't hurt to get in line at the airline's guest services counter at the same time, but with hundreds of passengers trying to reschedule and only a few agents on hand, you'll probably get quicker service on the phone. If you're stuck listening to hold music, head to the newest frontier in customer service: social media. Use Twitter to send a request for help to the airline. When you connect with an agent, whether by phone, in person or virtually, ask to be re-booked onto the next available flight to your destination.
The weather's mild, but your airline's having mechanical problems that will leave you grounded for hours: in this instance, you may have another option besides waiting around. Ask an airline agent if the company prescribes to Rule 240. Years ago, this rule guaranteed that an airline would book a passenger onto a flight carried by another airline, if the competitor's flight would get you there faster than its own next available flight would. Not all airlines follow this policy today, but it's worth asking. Inquire if your reservation can be transferred to the next outgoing flight scheduled by another airline at no additional cost to you. You can research your airline's policy in advance; read the company's "contract of carriage" for specifics.
When all flights are grounded, you have two options: head home, if you're flying out of your own hometown, or settle in until flights resume. If you opt for the former, call the airline every few hours for updates about rescheduled flights. If the latter is your only choice, ask an agent at the airline's guest services desk if you're eligible for food vouchers to use in the airport. Some airlines will pay for hotel rooms for non-local passengers stranded at the airport overnight due to a cancellation caused by something within the company's control. If flights are grounded due to weather, don't expect a free room, though a guest services rep might be able to help you locate a local hotel with vacancies.
When nasty weather looms and you know cancellation is a possibility, put yourself in a position to handle any issues smoothly. Check in for your flight online before leaving for the airport, if possible. When everyone's rushing to get onto flights before a storm, getting bumped could leave you stranded -- and airlines often determine who gets bumped based on check-in time, says USA.gov. Ditch the huge suitcase and pack everything in a carry-on bag. Not only will you have everything you need if you do get stranded, but you and your suitcase won't end up on different flights. Bring plenty of nonperishable snacks and entertainment options to pass the hours and save you from paying airport prices for food and books.