Cooperative Weather Observer Rainfall/Precipitation Measurement Refresher

Measuring Precipitation

The following instructions are intended as a refresher for Volunteer Cooperative Weather Observers who measure rainfall/precipitation.

Thank you for your continued support of the Climate Observations Program. As a Volunteer Cooperative Weather Observer, you are providing a valuable service which takes dedication on a daily basis. Your observations are used on a daily basis, recorded and will be available as historical records for many, many years.

Measuring rainfall/precipitation is a cornerstone of the observations program. At times, it is good to review the methods that are used to properly measure precipitation. Hopefully, a few pages of graphical examples will be enough to review and/or correct any measuring difficulties.

When measuring rainfall/precipitation, it is important to measure precipitation to the hundredths of an inch. Occasionally we will receive observations that are rounded to the nearest tenth of an inch or even rounded to the nearest one half inch. Precipitation measurements should never be “rounded”. The rainfall/precipitation measurement stick should be read as closely as possible to the nearest one hundredths of an inch (0.01) which means that we are measuring to the second place to the right of the decimal.

Measuring rainfall/precipitation to the hundredths of an inch is very important as historically, this is the resolution or precision of measurement that has been in place for over one hundred years.

The following pages show examples of how to measure using the rainfall/precipitation stick. If additional help or information is needed, please contact Rob DeRoy or Brad Fillbach at the National Weather Service Office at Des Moines. We will be more than happy to work with you to clear up any measurement questions you may have.

Again, thank you so much for being a Volunteer Cooperative Weather Observer. If you have any questions...please contact:

NWS Des Moines COOP Program Manager

Marvin A. Percha Jr.

1-800-759-9276

marvin.percha@noaa.gov

Measuring Precipitation with the 8" Standard Rain Gauge Measurement Stick