BOSTON – winter Come on, Boston. This Saturday, December 21st, is the official, astronomical start of the season, also known as Winter solstice.

At 4:20 a.m. Saturday, the Earth’s tilt will be furthest from the Sun in the Northern Hemisphere. The sun is directly above the Tropic of Capricorn.

Shortest day, longest night of the year

That means a few things: The sun will be at its lowest point in the sky and Saturday will be the shortest day of the year, with just nine hours and five minutes of daylight.

There are two ways to look at it: the glass half full or half empty.

Sure, we’re currently in the darkest days of the year, but there’s also the more optimistic approach: starting Sunday, we’ll get brighter every day until the summer solstice.

And the further north you live, the sooner you’ll have daylight again – something we can brag about to our friends who escape to Florida this time of year.

The winter solstice and perihelion

Here’s a strange fact to display on the Christmas table: Earth is actually closer to the sun during the winter solstice than it is in the summer.

Just a few weeks after the winter solstice, the Earth reaches perihelion (the closest point in its orbit to the Sun) and is at its furthest point (aphelion) in summer.

Our seasons have everything to do with the Earth’s tilt and not its orbit.

Coldest air of the season for Massachusetts

As if on cue, the coldest air The peak of the season so far will arrive this weekend at the solstice.

Temperatures are expected to remain below freezing across much of the Boston area Friday night through Tuesday morning.