If you can, keep your environmental sensors out of the RPI case.
As you have pointed, temperature, humidity and pressure readings from in will be really different than out. In summer here in the Mediterranean, you could fry an egg over a fully equipped OpenPlotter enclosure
Besides this if you can build a fully waterproof enclosure, pressure readings will be always the same, the pressure that was inside the enclosure when you closed it.
Connect all your I2C environmental sensors to the same 4 wires line. Make a small enclosure for them but remember, not completely sealed
As you have pointed, temperature, humidity and pressure readings from in will be really different than out. In summer here in the Mediterranean, you could fry an egg over a fully equipped OpenPlotter enclosure
Besides this if you can build a fully waterproof enclosure, pressure readings will be always the same, the pressure that was inside the enclosure when you closed it.
Connect all your I2C environmental sensors to the same 4 wires line. Make a small enclosure for them but remember, not completely sealed