Greenhouse agriculture is experiencing global expansion; however, in Andean countries such as Ecuador, its development is constrained by low-tech infrastructure, limited automation, and insufficient environmental monitoring, all of which negatively affect productivity and fruit quality. This study characterized the microclimate of a low-tech greenhouse in Chaltura, Imbabura Province, during a complete production cycle of tomato crop (Solanum lycopersicum L.). Microclimatic conditions were analyzed during three phenological stages (vegetative, reproductive, and harvest). Temperature and relative humidity were recorded at 5 min intervals using sensors placed in the greenhouse quadrants, while an external weather station provided daily outdoor climate data. Statistical analyses were performed in R software (version 4.4.x). The results revealed marked internal microclimatic heterogeneity and showed that the crop remained outside the optimal ranges of temperature, relative humidity, and vapor pressure deficit (VPD) for over 50% of the time across all phenological stages and greenhouse quadrants. These findings underscore the urgent need for cost-effective climate-control strategies adapted to local conditions and provide a scientific basis for future research aimed at improving climatic and productive efficiency, as well as the resilience and sustainability of protected agriculture in Andean regions.