Spring start date nears in Northern Hemisphere NBC Chicago [Video]

As we hit St. Patrick’s Day, spring is right around the corner in the Northern Hemisphere, even if it doesn’t feel like it judging by Chicago’s forecast.

Spring will get underway, at least from an astronomical perspective, later this week, according to the National Weather Service.

In fact, we even know the precise time when spring begins: 10:06 p.m. Central Daylight Time on Tuesday.

The reason we know the exact date is because the spring equinox marks a precise moment in time on the Earth’s revolution around the sun. As the planet moves, it does so at an angle, meaning that its axis is either tipped away from, or towards, the sun.

During fall and winter in the Northern Hemisphere, the Earth’s axis is tilted away from the sun, meaning that the Southern Hemisphere experiences more sunlight and therefore warmer conditions and longer days.

On the spring equinox, the planet’s axis makes the transition to …