Some other common factors which affect water consumption are indoor leaks, use of evaporative (swamp) coolers, air conditioning pre-coolers, leaking toilets and swimming pools. Routine maintenance & checking of this equipment can prevent leaks and other malfunctions that increase water use.
The most common cause of a spike in bills is irrigation. In the hot summer weather, it is expected that water usage will increase because of landscape irrigation. Watering times can double during the summer months compared to winter months. If you have an automated irrigation system, it's wise to check the valves & timer(s) periodically to be sure the system is functioning properly. If a sprinkler valve sticks on, it has the potential of wasting an extremely large quantity of water. You may also want to check for broken sprinkler heads or leaks in your irrigation system.