More than 460 cases of sarcoptic mange (Sarcoptes scabiei) in endangered San Joaquin kit foxes (SJKF; Vulpes macrotis mutica) have been reported in Bakersfield, California, US. Because SJKF are a den-obligate species, their dens have been proposed as a route of transmission. We determined whether SJKF den temperatures and humidities could support mite off-host survival based on previously published estimates of off-host mite survival times. We monitored SJKF dens for 6 d in summer and winter of 2017 and 2018 using temperature- and humidity-sensing data loggers placed within the dens. Motion-triggered cameras monitored animal use of and entrances into the dens. Linear regression models were fitted to the published mite survival data to predict estimated mite survival time (EMST) in SJKF dens based on observed mean temperature and humidity of the den. Den covariates including irrigation, type of den, and season were then fitted to a mixed effects linear model to predict EMST. The average EMST across various habitats in Bakersfield was 4.8 d; the longest EMST was 7.1 d for dens in habitats with irrigated grass in the winter. Den climatic conditions in Bakersfield may support off-host mite survival through a timeframe adequate for revisitation by another fox. The finding that irrigation may enhance EMST suggested that risk to foxes varied with den type and that mitigation strategies may need to vary with den types.