Learn more about us on our website.
Click logo for Flood Control's website.
Find the old rain gauge webpage here.
Questions about this web page/map should be directed to the
This site provides:
We collect the data from the stations every 20 minutes and update the map every 20 minutes.
Use the Datasets Menu to change rainfall period or select water level or battery voltage.
Use the Layer/Radar Menu to change which layer or radar product is shown.
This website works best in Chrome and Firefox. It may have display issues in Internet Explorer.
The NWS Radar Products (layers) are imported to this Gmap from the NWS and are not generated by the Contra Costa County Flood Control and Water Conservation District.
Detailed information about the layers can be found through the National Oceanic and Atmospheric Administration (NOAA).
Why does the N0Q radar mode show rain when it's not raining?
When it is not raining, the NOAA NEXRAD radars go into "Clear Air Mode" where their sensitivity increases. It then detects airborne dust and particulate matter. Rotating wind turbine blades can also impact radar readings. We see their impact in the the areas west of Rio Vista and around Altamont Pass. See this NOAA webpage for more information about wind turbines.
Go to the Legend for more information about the different radar layers.
If you are interested in how radar works, go to this website.
For a historic radar go to this website.
Clicking a blue "+" or a data label will open a window with station information, a table of data, and a plot.
The table cell colors for the 7-day, 30-day and Season amounts will change when the 7-5-3 protocols are met. See Flood Forecasting 7-5-3-2 in the Info menu list.
Storm rainfall resets at each gauge after 12 hours without rain.
The battery plots with flat voltage lines are for stations with batteries charged using household current. The battery plots with wavy voltage lines are for stations with batteries charged using solar panels. They gain or lose charge with the sunshine.
One of the most common station maintenance issues is battery charging failure which can be due to a variety of reasons.
The "Dataset:" and "Update:" text will turn red if it has been more than 1 hour since the last data update.
When the watersheds are wet, there is more chance of flooding when a big storm comes. We can look at past rainfall to get an idea of how wet the watersheds are.
A table pops up when you click on a rain data point (blue "+" or data number). The table shows you the rain that has fallen so far in the season, in the last 30-days, and in the last 7-days. When the rain depths are around 7", 3", and 5" respectively, and if we have a forecast of 2" of rain in the next 24 hours (see 24-hour QPF map), you should expect some level of flooding.
You can find out more about the 7-5-3-2 protocols at our Flood Forecast Information Page. Click the image below.
You may click the location marker to zoom in and center on it. It may be dragged to another location.
The location is not saved, but is updated to your current location on refresh.
The marker is an approximation of your location based on information from your device. The location is only as good as your device provides and may not be accurate or precise, and is only updated when you refresh the webpage. Sometimes a computer connected to a larger network will show a location of a main server for the system and not your computer.
CDEC is the California Data Exchange Center.
CDEC collects data from many different entities and station types. The Flood Control District sends its data to CDEC on a regular basis and various weather agencies use the data to proof their weather predictions and radar readings. Not all data sent to CDEC is corrected if we make adjustments to our data due to errors.
You will see links to the CDEC website at the bottom of the station popup menus. On mobile divices the CDEC Map link will not show since the map does not work well on mobile devices.
Note: The CDEC three letter tag is sometimes different than the Flood Control District three letter tag.
The data tool was developed to allow easier use of the data provided through links in the rain gauge popup windows. The tool was created in MS Excel, is open source, is not write protected, nor edit protected. The tool may be downloaded from the County website at the following link. It will help reformat the data in a more usable form.
This map was created from provisional data that has not been checked or verified for accuracy. This map was created solely for the convenience of the County and related public agencies.
The County does not warrant the accuracy of this map, and no decision involving a risk of economic loss or physical injury should be made from the data available on this site.