Mar 20, 2017 10:16 AM
Spring begins Monday; here's why NH already had 'equal day and night'
Spring began in the Northern Hemisphere at 6:29 a.m. EST Monday.
Known as the vernal or spring equinox, this is one of two days each year when the Earth’s axis is not tilted toward or away from the sun at all. This means day and night are close to equal length across the planet.
This also occurs on the autumnal equinox, which this year falls on Friday, September 22.
EQUAL DAY AND NIGHT?
It is not entirely true that day and night are exactly equal on the equinox. But it’s close. The shape of the earth is not perfect, which means not everywhere has “equal day and night” on the same date.
The earth is an oblate spheroid, a sphere that is squashed at its poles and swollen at the equator.
Ultimately, your latitude determines the exact day length.
In Concord, New Hampshire, the sun rose at 6:49 a.m. Monday and will set at 6:59 p.m. This means we have a total day length of 12 hours and 9 minutes, on the date of the equinox.
In Concord, the date with nearly 12 hours of daylight and 12 hours of darkness was actually March 17.
Image courtesy: AccuWeather.com
WARMER DAYS ARE AHEAD
Despite the snow still covering the ground, we can be certain that warmer days are ahead.
For the next six months, the days will be longer than the nights. We will continue to gain daylight until the first day of summer on June 21.
The average high temperature climbs from 45 degrees on March 20 to 79 degrees on the final day of astronomical spring, June 20.
The average low temperature rises from 24 degrees on March 20 to 54 degrees on June 20.
On average, the last frost in Concord occurs during the second week in May.