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The most common cause of any connection issues is from users not:

  • using Python 3
  • using the most up to date version of the CDS API

So before trying anything else we recommend you check these two issues.  If you're still experiencing problems the most frequent issues and fixes are below.

What type of error are you seeing?

'Timed out' or ‘Proxy’

If you're seeing an error message which mentions 'timed out' like the example below:


Timed Out

WARNING Recovering from connection error [HTTPSConnectionPool(host='cds.climate.copernicus.eu', port=443): 

Max retries exceeded with url: /api/v2/tasks/7b4e735b-5a79-4913-bbcb-cebc0c65b420 (Caused by ConnectTimeoutError(<urllib3.connection.VerifiedHTTPSConnection object at 0x7f81056e8940>, 'Connection to cds.climate.copernicus.eu timed out. (connect timeout=60)'))], attempts 12 of 500



Diagnosis: This is likely due to network issues causing delays in the communication between the your system and the CDS.

Solution: The best way round this is to add the "timeout=600" (or longer) option for the timeout duration in seconds, to your CDS API request :

c = cdsapi.Client(timeout=600,quiet=False,debug=True)



If the message mentions ‘Cannot connect to proxy’ 

WARNING Recovering from connection error [HTTPSConnectionPool(host='cds.climate.copernicus.eu', port=443): Max retries exceeded with url: /api/v2/resources/cems-fire-historical (Caused by ProxyError('Cannot connect to proxy.', timeout('_ssl.c:835: The handshake operation timed out',)))], attempts 0 of 500


Diagnosis: This could also be due to the network issues causing delays in the communication between the your system and the CDS.  Therefore we recommend to try this solution first  

Solution: Add the "timeout=600" (or longer) option for the timeout duration in seconds, to your CDS API request :

c = cdsapi.Client(timeout=600,quiet=False,debug=True)

If the issue continues you will need to check that the ports required by the CDS are open on your firewall (i.e. https,  443)


If the issue persists please contact ECMWF support via …… button