# How to Calculate Average Monthly Rainfall

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Knowing the average monthly rainfall for a location is helpful when you're packing for a trip or considering relocating your family. Or maybe you just want to know how much it rains in your back yard. Finding the average monthly rainfall in any location is a relatively simple and straightforward calculation if you have the proper data.

## Calculating From Provided Data

Gather the monthly rainfall data for the desired location from a website such as the National Climatic Data Center. Because of year-to-year fluctuations in precipitation, you'll want to gather at least 10 consecutive years of data for any one month to give you a better idea of the location's monthly average.

Add together all of the monthly rainfall totals in your sample data. You'll be adding measurements in inches because rainfall is generally measured in inches in the United States.

Divide by the number of years in your data set to arrive at the average monthly rainfall for any location. An example of the complete calculation for a 10-year average monthly rainfall should look like this: 3.2 (inches of rain) + 3.1 + 2.9 + 3.7 + 2.9 + 4.1 + 3.5 + 2.8 + 2.9 + 1.7 = 30.8 inches of rain, divided by 10 years = 3.08 inches of average monthly rainfall.