Weather.com

Weather.com is an easy-to-use source for precipitation data.  However, they only display data from the current month and the previous month.  Furthermore, the nearest weather station may not be close enough to your monitoring site to be considered accurate.

1. Go to http://www.weather.com.
2. Type in your zip code, city, or place.
3. Locate the blue tabs.
4. Select "Month."

Weather Underground

This is a good source for data older than one month, and it may be more likely you will locate a station closer to your monitoring site because more stations are included.  It is not as easy-to-use as weather.com though.

1. Go to http://www.wunderground.com.
2. Enter your zip code or city.
3. Scroll down to locate the "History & Almanac" section.
4. Toward the bottom of that section, locate and click "Calendar View."