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Authorization

Follow this guide to create a new CIMIS API credential that will allow Nexla to authenticate to and exchange data with your CIMIS account.
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CIMIS API

Prerequisites​

To use the CIMIS Web API, you need a registered CIMIS account and a Web API AppKey. The AppKey is a unique application key that authenticates your requests to the CIMIS data services. CIMIS data access is free of charge, and registration is straightforward.

Register for a CIMIS Account and Obtain an AppKey​

  1. Navigate to the CIMIS website at https://www.cimis.water.ca.gov and click the Register link to create a new account.

  2. Complete the registration form with your name, organization, email address, and a password. After submitting the form, you will receive a confirmation email at the address you provided.

  3. Confirm your email address by clicking the link in the confirmation email to activate your account.

  4. Log in to your CIMIS account at https://www.cimis.water.ca.gov using your registered email and password.

  5. Once logged in, navigate to your Account page and scroll to the end of the page.

  6. Click the Get AppKey button to generate your Web API application key. Your AppKey will be displayed on the page.

    Copy your AppKey immediately and store it securely. Your AppKey authenticates all API requests to CIMIS data services. Treat it like a password and do not share it publicly.

Note on API Transition

The CIMIS Web API at et.water.ca.gov will remain operational through July 31, 2026, running in parallel with the new CIMIS system. Registered users will be migrated to the new system and will receive an email with a temporary password and instructions. For additional information, visit https://www.cimis.water.ca.gov.

Create a CIMIS API Credential​

  • To create a new CIMIS API credential, after selecting the data source type, click the Add Credential tile to open the Add New Credential overlay.

Credential Name & Description​

  1. Enter a name for the credential in the Credential Name field and a short, meaningful description in the Credential Description field.

    Resource descriptions are recommended but are not required. They should be used to provide information about the resource purpose, data freshness, etc. that can help the owner and other users efficiently understand and utilize the resource.

API Key​

  1. Enter your CIMIS Web API AppKey in the App Key field. This is the application key you generated in the Prerequisites section above. The AppKey is passed as a query parameter with every API request to authenticate your access to CIMIS data services.

    Your AppKey provides access to all CIMIS weather station data, spatial ETo data, and zip code data services. Ensure you are using the AppKey associated with your registered CIMIS account.

Save the Credential​

  1. Once all of the relevant steps in the above sections have been completed, click the Save button at the bottom of the overlay to save the configured credential.

  2. The newly added credential will now appear in a tile on the Authenticate screen during data source creation and can be selected for use with a new data source.