@rharte the Ruuvi mentioned somewhere above here is using a BME280 sensor and has an IP67 case - however, it’s not a TTN node, data is transmitted via BLE.
I ordered one but did not get to test it extensively yet. What I can say so far is, it works well under indoor conditions. In any case, the housing has a whole that is protected by a Gore membrane. There’s no additional protection of the circuits.
The Laird device mentioned by Jeff is protecting the sensor in a similar way - but - does not expose the whole electronics to humidity, which is the better solution in my view. I have been testing the Laird for several month now. Temperature accuracy is good, to measure humidity under cold and humid weather conditions became a problem. Seems sooner or later you will have condensate on the sensor, does not matter which sensor it is. Laird support advised me to use the heating element of the Si7021 in order to mitigate this - which I did not have time to try yet.