A probe style radiometer includes a generally rectangular cross-sectional body and a probe having a square cross-section. The probe is preferably a hollow rod having a tip equipped with a UV-collecting aperture and a mirror. The mirror reflects UV light entering the aperture down the length of the rod to a detector in the body. A processor in the body then computes the amount of UV radiation based on signals from the detector. The amount may then be provided on a display integrated into the body. A ground quartz or glass window may be provided at the tip to seal the rod from exterior contamination and to diffuse the incoming UV radiation in a manner that will give the probe a near-cosine angular response. Filters within the radiometer body then filter this diffused radiation to the spectral region of interest. Preferably, the radiometer is battery powered and includes switches on the body to allow a user to control the mode of operation. To prevent electrical shock, the metal rod of the probe may contain an electrically non-conductive outer coating.