What happens to my ticket if a session is cut short by weather or other events?

From the National Bank Open's Rain and Cancellation Policy (applies to tickets bought directly from Tennis Canada or Ticketmaster; the policy covers extreme heat, poor air quality, protests, authority alerts or directives and other events beyond the organizers' control):

• A session counts as complete once one match is completed or 90 minutes of play has taken place. After that there are no exchanges, credits or refunds.
• If a session has less than one match and less than 90 minutes of play, eligible tickets can be used as a credit (excluding processing and delivery fees) toward a future session of the same year's event, subject to availability. You pay any price difference and keep the original tickets, and credits expire after the period the Box Office specifies.
• Toronto: "all sales are final, there are no refunds". Montréal: no exchange or refund is possible for postponed sessions 17 to 21.
• Schedules, start times and session dates can change without notice and do not qualify for exchanges or credits.
• Exemptions in Montréal include certain court packages, complimentary tickets, resale tickets, sessions 17 to 21 and ground passes. In Toronto they include Series tickets, Chairperson's Lounge tickets, complimentary tickets and resale tickets.
• Private suites stay open during rain, and part of a paid suite ticket may be credited for next year's event.