How will heavy rains change in western Washington?

How will heavy rains change in western Washington?

Project Details: Regional Model Projections of Heavy Precipitation For Use In Stormwater Planning

The visualization below allows users to browse changes in precipitation for two new regional climate model simulations, described on this page shows projected changes in precipitation for two future time periods in three regions in the Pacific Northwest.

How to use this tool

This heavy precipitation tool was created using Tableau. The tool includes three panels: (1) Percent Changes, (2) Intensity-Duration-Frequency Curves, and (3) Model Validation. The layout of the tool is illustrated in the figure below. The main purpose of this tool is to allow users to browse changes in precipitation for two new regional climate model simulations, described on this project page. The tool provides information on the projected changes as well as comparisons with observations for a number of precipitation durations, seasons, future decades, and return frequencies. The three tabs provide different ways of getting at this information.

Tool Menus and Options

  • Network: This menu refers to the observational network from which the observations were obtained. Currently, the tool includes observations from the NOAA Cooperative Observer (COOP), King County, Seattle, Everett, and Thurston County rain gauge networks.
  • Station: This menu refers to the specific rain gauge station within each network. For example, the Sea-Tac rain gauge station is operated by the COOP network. In the first two tabs, this menu allows you to view results that are specific to a particular rain gauge of interest. To view a map of all stations included in the current tool, users can consult this Google map.
  • Water Year or SeasonWe computed precipitation statistics for both the entire water year (Oct-Sep) as well as the four seasons (winter: Dec-Feb, Spring: Mar-May, Summer: Jun-Aug, Fall: Sep-Nov). Use this menu to select which one you would like to view.
  • Duration: This menu refers to the precipitation duration for which you would like to view our results. We evaluated precipitation for 11 different durations ranging from 1-hour to 360-hour (15-day) totals.
  • Metric: The tool includes extreme precipitation statistics for the 2-, 10-, 25-, 50-, and 100-year events. These were computed using the standard block-maximum approach and fit to a Generalized Extreme Value (GEV) distribution using L-moments (see the reports on our project page for more details). In addition, we have computed the total precipitation for each season and water year for comparison with the results for extreme precipitation.
  • Scenario: Two regional climate model simulations are included in the tool. One is intended to provide a high-end estimate of changes in heavy precipitation, and was produced using results from the GFDL CM3 global climate model and the high-end RCP 8.5 greenhouse gas scenario. The other is intended to provide a low-end estimate of changes in heavy precipitation, and was produced using results from the ACCESS 1.0 global climate model and the low-end RCP 4.5 greenhouse gas scenario. As above, this is described in more detail on our project page.
  • Decade: The Regional Climate Model simulations were initiated in 1970 and run through 2099. We computed precipitation statistics for one historical (1980-2009) and three future 30-year periods (2030s: 2020-2049, 2050s: 2040-2069, 2080s: 2070-2099).
  • Units: In the Intensity Duration Frequency tab, an option is included to toggle between metric (mm/hour) and imperial (in/hour) units.

Reference Data

Additional information can be found on our project website, including links to our reports on these new projections, a Google map showing the locations of the stations, and an online repository for obtaining the results.


The primary source of funding for this work was the King County Department of Natural Resources and Parks. Additional funding was provided by the Washington State Department of Ecology, City of Everett, Thurston County, and the Port Gamble S’Klallam tribe.


 Please contact Guillaume Mauger ( with any questions about this project.


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