Overview

• The equinox starts astronomical fall in the Northern Hemisphere and spring in the Southern Hemisphere.
• Day and night are not exactly equal today due to atmospheric refraction and sunrise/sunset conventions, with the true equilux occurring several days later depending on latitude.
• Regional foliage forecasts point to an earlier show, with peak color in the Philadelphia area expected around Halloween into early November.
• Southbound bird migration over the Philly region is set to crest from late September into the first week of October, highlighted by chimney swifts and broad‑winged hawks.
• Night skies will brighten with near‑full “supermoons” on Oct. 6, Nov. 5, and Dec. 4, and equinox periods statistically favor aurora at high latitudes though sightings remain unlikely this far south.