[PHXFlyer]

I'm surprised they even used the pretense of "weather" because their Contract of Carriage doesn't differentiate. The information is in the above linked posts but here are the relevant clauses from Spirit's COC:

Delayed and Canceled Flights

1. Rebooking When a ticketed passenger holding a confirmed reservation on a flight will be delayed because of a schedule irregularity (including but not limited to, a missed connection, flight cancellation, omission of a scheduled stop, substitution of equipment, a different class of service or schedule change), Spirit will rebook the passenger on Spirit's first available flight to the passenger's destination without additional charge.
2. Amenities/Services for Passengers Spirit will not assume expenses incurred as a result of a flight delay, cancellation, or schedule change. Spirit may provide limited amenities and services, which may be required by certain passengers in order to maintain their safety, health and welfare. Amenities provided by Spirit are provided as courtesy to the customer and are not to be considered an obligation of Spirit. No lodging will be provided to a passenger on any Spirit flight, which is delayed or canceled in the city of the passenger's residence.

As you can clearly see if Spirit cancels a flight all they owe you nothing except rescheduling you on the next available Spirit flight. For a refund you will probably need to file in small claims court.

Good luck.