If it is only a humidity sensor, then the potting compound outgassing shouldn't poison it. VOC sensors are much more sensitive. I would call the manufacturer of the sensors and ask technical support what they recommend to use.

EDIT: Silicone based compounds can poison many of your sensors! Use epoxy based potting compounds. Again, I would call the manufacturer of the sensor for guidance.

Thank you :)

Block out ambient sensors and your antenna w/ foam to keep out the potting compound. You can also use a gore-vent on the ambient sensors to prolong lifespan. I would also suggest spending some time choosing your battery chemistry. It sounds like you will be freezing and thawing which can reduce the lifespan of lithium cells.

A humidity sensor, coated with conformal coating, will simply not function properly.

If you need conformal coating on your PCB, most sensor manufacturers will recommend you to cover the top of the sensor with some material (for example, Kapton tape), apply conformal coating to the PCB, and then remove the tape.