Southwest Airlines is experiencing relatively few flight delays and cancellations while they are proactively inspecting some Boeing 737s. For more information about these inspections.
If your flight is delayed or canceled and you would like to reschedule your trip in accordance with Southwest accommodation guidelines Online Rebook
For Customers who did not purchase their ticket via southwest.com, please call 1-800-435-9792 to rebook your travel plans without paying any additional charge. Also, Customers holding reservations for a canceled flight may request a refund for an unused ticket/travel itinerary.
Link to ehow article on Southwest Cancellation policy.