Dropping temperatures can cause pipes to freeze and burst. If you label the main shutoff valves ahead of time, you'll know exactly which ones to turn off to avert flooding. Print the name of the water source on a peel-off label (or use a personal label maker). Affix the labels to copper plant tags, and wrap them around the appropriate pipes.
Wow! What a simple but brilliant idea! This would be especially wise to do if you own any sort of rental property, so tenants can prevent a mess if you or your plumber can't get out to the property immediately.
never thought of this - I live in an older rental w/ pipes in the basement