WEATHER WHY: Sunlight on the Equinox

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A viewer asks why we had 12 hours and 10 minutes of sunlight on the spring equinox, instead of exactly 12 hours. Megan explains that the equinox is actually based on the time from the center of the sun rising over the horizon to the center of the sun setting over the horizon. Sunrise and sunset times are based on the sun's first appearance over the horizon. This plays a part in the extra minutes of sunlight on the equinox. Refraction also plays a part. As the light refracts through our atmosphere, we see the sunlight a few minutes before the sun actually rises above the horizon.