The humid summer weather in North Carolina places extra stress on a home air conditioning system. An AC has to run longer to overcome the additional discomfort that high humidity creates. (An air conditioner isn’t a dehumidifier, however. To deal with serious humidity issues in a home, we recommend you have a dedicated whole-house dehumidifier installed.)
One of the ways that all this extra moisture in the air affects an air conditioner is that it collects along the indoor evaporator coil as the AC is running. This moisture has to go somewhere, so an AC is designed with a condensate pan and drain to catch the dripping moisture and then pump it outside. The occasional sound of water running in the AC cabinet is this condensate system at work.