I designed this 3D model to provide basic protection against the elements for an outdoor Zigbee temperature and humidity sensor.
 

I printed the model in ABS, but other materials should also work well depending on your environment and requirements.
The parts 0, 1, 2, 3, 4 and bracket can be printed without support. Only the sensor holder and top cover needs support.
 

Parts 1, 2, 3, and 4 are (identical) mounted onto Part 0 using a small amount of glue. Part 5 is glued on top. 
The sensor holder can optionally be glued to the bracket, but it also fits securely without adhesive. 
The top cover is attached to the bracket using a screw connection, allowing easy access to the sensor later for battery replacement.
 

If you want to use a different sensor that does not fit the standard sensor holder, I have included an additional part called “sensor holder flat (extra)”.

My own sensor, recognized by Zigbee2MQTT as TH09Z, measures 27 × 23 × 74 mm. The enclosure provides space for sensors up to 75 mm in height and 37 mm in diameter (round).

The mounting holes for attaching the bracket are 4.5 mm in diameter.