Trying to identify a Breaker in my electric panel...

While it could be the extension cord, there is a very good chance its the lack of a good cover at the receptacle.
Vertical cover link

There is both a vertical and horizontal cover in the listing. They are designed to keep water off of your receptacle. They are required for continuous use, however they protrude causing a new problem.

there is a low profile cover but may not be deep enough for your cord?
Taymac MX4280WH