If this just happened and water is pooling on the drywall---Get a screw driver and poke some holes to drain the water.
If the sheets of drywall are sagging or look really wet----cut open the ceiling to allow air to circulate and dry it out. Get fans and a dehumidifier going.
If there is no sagging and the staining doesn't look to bad---get some fans and a dehumidifier going
run your air conditioner,also(that is a dehumidifier,too)
Take a picture if you can and post it.----Mike---
New members: Adding your location to your profile helps in many ways.--M--