Precipitation - Monthly Total

Colors show monthly precipitation totals for each of the 344 climate divisions in the contiguous United States. The darker the color, the higher the total precipitation.

Daily measurements of rain and snow come from weather stations in the Global Historical Climatology Network. For each station, climate scientists check the data quality, calculate the monthly total, and plot it on a gridded map. To fill the grid, a computer program applies a mathematical filter that accounts for the distribution of stations and the terrain. The total precipitation for each climate division is the average of all grid point values that fall within it.

Climate divisions shown in white received little or no measurable precipitation for the month. Areas shown in the lightest green received less than one inch of water from rain or snow. The darker the color on the map, the higher the precipitation for the month. Areas shown in dark blue received 8 inches or more of precipitation  that fell as either rain or snow.

Farmers and gardeners who depend on rain for their plants want to know if enough precipitation has fallen to support plant growth. Similarly, forest managers and ranchers check monthly precipitation to monitor the status of the environment. Water managers who work to ensure that towns and cities have enough water for drinking, washing, and industrial uses are also interested in how much precipitation falls each month.

Data Snapshots are derivatives of existing data products: to meet the needs of a broad audience, we present the source data in a simplified visual style. This set of snapshots is based on climate division data (nClimDiv) produced by and available from the National Centers for Environmental Information (NCEI) - Weather and Climate. To produce our images, we invoke a set of scripts that access the source data and represent them according to our selected color ramps on our base maps.