Spring is a glorious, warm season after the harsh cold of winter—filled with light and more sun-induced vitamin D. Friday, March 20, 2026 (at exactly **10:46 a.m.** ET), marks both its triumphant return in the Northern Hemisphere and the spring equinox. So, get ready for longer days, warmer weather, and flower blooms that may cause sneezing. Let’s take a deeper look at the science behind seasons and what exactly an equinox is. ## What causes the seasons? The tilt of the Earth’s axis as it orbits around the sun is what causes seasons. Depending on that angle, different parts of the world receive different amounts of sunlight. In the Northern Hemisphere, we experience winter from December to March, while the Southern Hemisphere soaks up the sun. They get their turn to be cooler during our summer—in June, July, and August. ## Why does the first day of spring fall on different days? Even though a year is 365 days long, it actually takes 365.25 days for the Earth to travel around the sun.…