Be sure to use the lower charged primers, those made to shoot pellets. Keep your powder (pellets) dry. I don't believe it was mentioned, but was it a powerbelt you were using? Make sure the bullet is seated securely on the propellant, but don't crush the pellets.
Being from FL with high humidity, I'd most likely cover the barrel with a balloon to keep the humidity out. Not obstruct the barrel, but a balloon over the barrel will break, yet help to keep out humidity.