Water Evaporation: The effects of humidity
When humidity is nearly 100% outside, the water in your toilet can evaporate (even with the air conditioning on). For seasonal homes, this is a concern, because the water in a toilet bowl or drain trap in the shower can dry up, allowing sewer gases (and even some living creatures!) to come up through the drain. If your home will be vacant for several months, consider putting plastic wrap over the seat, cap sinks and tubs, or even hire a home watch representative to come in occasionally and flush/run water down the drains.
Save water! Newer toilets are more efficient. Older models require 3-5 gallons per flush (gpf), whereas newer models only require around 1.6 gpf.