Depends on the weather and your personal threshold. We've had 70+ temps in January and had no problem swimming. It should be even warmer than that on many March days. It's probably not anything you can schedule far in advance--you'll just have to keep an eye on the forecast after you arrive and pick a good day.
All Disney resort pools and waterparks have heated water.
Also FYI, I'm not sure that Typhoon Lagoon will be open when you are there. It closes for rehab every winter, and I think this year's rehab is scheduled to run at least into March. But Blizzard Beach should be open daily, as well as the resort pool.