Early Sunday marks the final hours of astronomical fall and the start of astronomical winter, or the winter solstice, which is at 10:03 a.m., Sunday this year. It is also the longest night of the year.

Behind the mild day on Friday will come a colder one for Saturday. But this is very short-lived and certainly not a very intense cold. Temperatures will start in the 20s and end up in the 30s to low 40s as warmer air will already be streaming into the region. You’ll notice some high clouds in the afternoon, along with a light wind, a marker of warm air advection.

Some snow showers will brush through Northern New England on Saturday.

Saturday night, a light southwest breeze will keep temperatures from falling too much, holding to around 30 all night long.

With that sort of a springboard, readings on Sunday will reach into the mid-40s along with a blend of clouds and sun.

Cold air drives in behind Sunday’s milder temperatures for a cold start to Christmas week.

Looking further ahead, there’s a small chance of some snow in the couple of days before Christmas. Whether or not we would end up with an inch on the ground in Boston on Christmas morning is still unlikely, but it’s not a zero chance.

Greater Boston: Look for plenty of sunshine on Saturday with temperatures in the mid- to upper 30s. A blend of clouds and sunshine is on tap for Sunday with temperatures in the low to mid-40s.

Central/Western Mass.: Look for sunny skies with temperatures just about freezing on Saturday and a little bit of a breeze. It’s near or a little above 40 and blustery on Sunday with partly sunny skies.

Southeastern Mass.: Temperatures will reach the low 40s on Saturday with mostly sunny skies and a bit of a westerly breeze; it’s in the mid- to upper 40s on Sunday with sun and clouds.

Cape and Islands: Temperatures will reach the low 40s on Saturday under an abundance of sunshine. Some clouds mixed with the sun on Sunday, with temperatures in the mid-40s.

Rhode Island: Mostly sunny on Saturday with highs in the low 40s, then on Sunday, look for partly sunny skies and highs in the mid-40s.

New Hampshire: Look for a dry weekend with temperatures right around freezing on Saturday under sunny skies and near 40 on Sunday with partly sunny skies. It will be colder in the mountains by about 10 degrees.

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This time, the people marched in resistance to the harsh treatment of immigrants by the Trump administration.

“We descend from Immigrants and Revolutionaries,” read a battle cry beamed onto the side of the brick meeting house Tuesday.

“The society that stops seeing the people at the grocery line or the people that ride the bus with us, as human beings with beating hearts, then it’s not far off before our society devolves into no society at all,” Gilberto Calderin, director of advocacy at the Massachusetts Immigrant and Refugee Advocacy Coalition said to the crowd of hundreds.

The protest was organized by activist groups Boston Indivisible and Mass 50501, and began at the Irish Famine Memorial Plaza, just steps from the meeting house.

The lively crowd held up signs, waved American flags, and chanted during the march along Milk Street and Congress Street to the harbor.

Janet England of Brighton held a sign that read, “Democracy Needs Courage.”

The protesters, she said are “true patriots because we want freedom and democracy.”

“Although protest is a long game, we can’t give up. If you think about women’s suffrage, gay rights, the civil rights movement, it took years, but we just can’t give up,” she said.

Gloria Krusemeyer, from Alrington, used a walker to join the march.

“I’m irritated that I haven’t done more, and I’m just lucky that I can walk fast enough to be doing this,” she said.

Rick Mueller, from Cambridge, was dressed as Uncle Sam and held a large sign that read, “Liberty and Justice For All.”

“We’re fighting for America, so I’m gonna be America,” he said of his costume.

He handed small American flags out to protesters who waved them enthusiastically.

Ice dumping duties was limited to volunteers and select people.

Among them was Sarah, a mother who brought her 4-year-old daughter, Fiona.

Sarah declined to share her last name for her daughter’s safety.

After throwing ice into the harbor, Fiona shyly said that she wanted to come to the protest to “help families stay together.”

Through tears, Sarah said her decision to bring along Fiona came from wanting to teach her daughter to care about people from all walks of life.

“Kindness and compassion are things we learn in kindergarten and she will be in kindergarten so it’s really important for her to be kind and compassionate,” Sarah said, kissing her daughter’s check.

Likewise, Sara Sievers, from Cambridge, brought her parents, sister, her nephews and niece to dump ice.

“I think this is one of the most brutal regimes we’ve had in this country, and I want my niece and nephew to remember that it’s important to protest, and that we in Boston are part of a proud tradition of dumping things into the harbor with which we disagree,” Sievers said.

The family wore costumes of historical figures including Abigail Adams, Thomas Jefferson, and King Charles.

As the protest came to a close, Martha Laposata, spokesperson for Boston Indivisible said she wanted protestors to walk away knowing their voices matter.

“We cannot stand down,” Laposata said. “When people rise up against an authoritarian government, if they stay consistent and they keep growing, ultimately an authoritarian government will stand down.”

Camille Bugayong can be reached at camille.bugayong@globe.com.

An MIT professor was shot and killed in Brookline on Monday night.

Brookline police responded a report of a man shot in his home on Gibbs Street, according to the Norfolk County District Attorney’s Office.

Nuno F.G. Loureiro, 47, was transported to a local hospital and was pronounced dead on Tuesday morning, the DA says.

Loureiro was the director of MIT’s Plasma Science and Fusion Center and a professor of nuclear science and engineering and physics. Originally from Portugal, the Portuguese Minister of Foreign Affairs announced his death in a regulatory hearing before the Committee on Foreign Affairs and Portuguese Communities on Tuesday, according to CNN.

“Sadly, I can confirm that Professor Nuno Loureiro, who died early this morning, was a current MIT faculty member in the departments of Nuclear Science & Engineering and Physics, as well as the Director of MIT’s Plasma Science and Fusion Center. Our deepest sympathies are with his family, students, colleagues, and all those who are grieving,” an MIT spokesperson wrote in a statement.

In January, Loureiro was honored as one of nearly 400 scientists and engineers with the Presidential Early Career Award for Scientists and Engineers from former president Joe Biden.

The investigation into the homicide remains ongoing. No further information was released.