This is a solar shield shroud to be used with any of the many available temperature probes that come with digital thermometers.  It will shield the probe from most of the heat created by direct sunlight on the probe, and therefore allow a more accurate reading of air temperature.  The probe is inserted from the bottom as shown in the photo.

While there are other solar shield models available, I was looking for a small one that could be printed as a single unit.  Most of the others are assembled from multiple layers and require additional hardware.  This is a single unit that can be printed in place, with no supports needed.

It's recommended to print using ASA filament.  Since the intended use is outdoors in direct sunlight, UV from the sun will degrade most other plastics.  ASA is highly UV resistant.