The ecological nesting requirements of Northern Black Swifts (Cypseloides niger borealis) have been well documented, but little information exists regarding the microclimate at Black Swift nests. We placed 42 data loggers at 10 occupied Black Swift colonies between 2006 and 2010 to measure and record temperature and relative humidity, resulting in 19,181 usable records. Median temperature and relative humidity at nine Colorado and New Mexico sites were 9.4 °C and 89.7%, respectively, and at one California site were 13.4 °C and 92.8%, respectively. Values were quite stable throughout the breeding season with slight changes reflecting the ambient temperature and humidity of the surrounding macroclimate. These baseline data may prove useful for conservation of this species, especially if predicted global climate changes occur.