From First Frost to Last Snow: Tracking the Microclimate Evolution of Greenhouses Across North China’s Winter Spectrum

Global climate change has intensified the challenges of low-temperature, low-light, and high-humidity microclimates in North China’s greenhouses during winter, exposing the limitations of traditional controlled-environment agriculture (CEA) facilities. This study monitored air temperature, relative humidity, and light intensity in three greenhouse types—an externally insulated plastic greenhouse, soft-shell solar greenhouse, and brick-walled solar greenhouse—across three overwintering periods (pre-, mid-, post-) using high-precision sensors (monitoring period is from 1 October 2024 to 31 March 2025). A Comprehensive Evaluation Index (CEI) based on the entropy method was developed, integrating seven indicators (daily average temperature, temperature range, hours below 5 °C, average humidity, hours above 80% humidity, average light intensity, and light utilization efficiency) to systematically evaluate greenhouse microclimate regulation performance. Results showed that the brick-walled solar greenhouse exhibited superior thermal insulation, with nearly zero hours below 5 °C during mid-overwintering, while the soft-shell solar greenhouse achieved the highest light utilization efficiency (75.1–79.6%). The externally insulated plastic greenhouse exhibited the highest relative humidity (>80% for 13–19 h/day) but a poor thermal insulation performance. The CEI ranked the brick-walled solar greenhouse (0.86) and the soft-shell solar greenhouse (0.84) significantly higher than the externally insulated plastic greenhouse (0.39), with the relative humidity significantly negatively correlated with light indicators (<i>P</i> < 0.05), and the temperature and light indicators strongly correlated with the CEI (<i>P</i> < 0.01). Structural design and material innovation are critical for climate adaptation. Brick-walled and soft-shell solar greenhouses balance thermal and light performance, while the externally insulated plastic greenhouse faces structural limitations. The findings provide a scientific basis for greenhouse optimization and regional layout planning.