Drying time depends on several factors such as how dirty the carpet is, the humidity in the home and the weather outside.
Typically carpets dry on the same day that they were cleaned. Some carpets can take up to 24-hours to get completely dry. While cleaning when it is raining out is never ideal for the customer, it does not cause the carpets to dry any slower. However, a sunny, warmer day does help speed up the drying time because you can open the windows and doors to get a nice circulation of air moving through the home. In any situation a fan is the best tool to help the carpets dry faster.