Contra Costa County

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Contra Costa County Boundary

All County Boundaries

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 Menu or Radar Button to change which layer show an turn on/off the Radar.

This website works best in Chrome and Firefox. It may have display issues in Internet Explorer.

The NWS Radar Products are imported to this RainMap are not generated by the Contra Costa County Flood Control and Water Conservation District.

Why does the radar 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. This mode 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.

High Resolution Rapid Refresh (HRRR): This is a new forecast product from the NWS that is being perfected and implemented in many forecast products. Find out more about HRRR at the HRRR website. See also a HRR Radar Map by others.

If you are interested in how radar works, go to this website.

For a historic radar go to this website.

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.

Forecast Info

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.

Rainfall, Water Level, and Battery voltage
marker = No precipitation has occurred in the select time period.
marker = Data missing, gauge has not reported in last 24 hours.

Point color: Point color will change when 7-5-3 protocols are met. Click 7-5-3-2 menu or icon for more information.

Radars: The Radar layer provides a view of the relative rainfall intensity. See also the "Radar Info" button under the "More" menu.