The Southern Wide-field Gamma-ray Observatory (SWGO) project aims to build an array of air-shower detectors in the Southern hemisphere. Intensive site search activities are ongoing. We developed an Autonomous Environmental and Scientific SWGO Site Characterization Instrument (AEROSITE) to measure environmental characteristics of the proposed sites and deployed four of them in Argentina, Bolivia, Chile and Peru. The instruments are located at very high altitudes of more than 4500 m.a.s.l. We completed an intensive cross-calibration campaign to validate the performance and sensitivity of all AEROSITEs in 2020 and installed the instruments at the sites between October 2021 and April 2022. The instruments are gathering important data without any major issues. At some candidate sites, non-SWGO environmental monitoring systems are also available. In this case, the AEROSITE serves as a cross-calibration instrument to allow a possible extension of the data points to the past using the available data sources. On the other hand, the AEROSITE data are important for designing the SWGO detectors using the real conditions at the sites such as temperatures, wind, electric field and seismic activity.