Dealing with condensation in outdoor projects

I replaced a Photon that had been running for several years outdoors in a Tupperware container with a hole cut out of the bottom for the power and sensor wire to go through. Overtime it literally fell apart, holes everywhere, spiders inside, etc. So I replaced it with a Xenon with a battery inside a sealed screw top jar. I used a grommet to allow the sensor wire through but to keep it water proof. After a recent rainstorm the Xenon was dead, corroded with water on the circuit board and a few drops at the bottom of the container. So I figure this was due to condensation, with the temperature based pressure changes to pull in the humid air and the Xenon not generating enough heat internally to keep it dry. The container had last been opened and everything looked fine less than 1 week ago, it died after 2-3 days of cool temps and rain storms.

Wondering if there are best practices on how to prevent this from happening again? Perhaps purposely allow for air exchange and have a drain hole? Maybe do a better job at making the container air tight and include a desiccant?

Also curious if anyone knows enough to speculate more how it died and the time frame. For example if I had an internal humidity sensor and it was reading very high, would I have a few days to fix it or would 1 night of condensation kill the Xenon. Anything that might help me catch this issue before I lose another device; assuming there’s no idiot proof sure-fire solution. Thanks in advance.

For a 1-off situation, I’d use a Silicone Conformal Coating (sample link).

A proper enclosure would obviously help.
There are methods and products to replace the ambient air with other gases when you seal the enclosure.
Also, it might help to keep your air volume as small as possible.

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A few years back there was a similar discussion on this forum which also suggested to use some Goretex like air vents.
Maybe there you can find some more ideas.