The spring equinox - also known as vernal equinox - marks the first day of spring in the northern hemisphere, according to the Old Farmer's Almanac. It occurs when the sun is directly above the equator, resulting in nearly equal daylight and night hours.

Spring starts on Thursday, March 20, when the vernal equinox marks the start of the astronomical season.

While temperatures are heating up and desert flowers are starting to bloom, astronomical spring won't start until later in the month.