| Season | Start (Astronomical) | Characteristic Day Length | |--------------|----------------------|---------------------------| | Spring | March equinox | Increasing daylight | | Summer | June solstice | Maximum daylight | | Autumn | September equinox | Decreasing daylight | | Winter | December solstice | Minimum daylight |
The Northern Hemisphere season is a product of Earth’s geometry—specifically its axial tilt—modulated by land-ocean distribution and atmospheric circulation. While astronomical solstices and equinoxes provide fixed boundaries, meteorological definitions offer practical utility for science and society. Observational evidence clearly indicates that anthropogenic climate change is shifting seasonal timing and intensity, with profound implications for ecosystems, agriculture, and human health. Continued monitoring and modeling of seasonal parameters are essential for adaptation strategies. northern hemisphere season