Here's what's happened at the 128th Boston Marathon

A sunny and warm spring day brought spectators out to the Boston Marathon's sidelines to cheer on the runners.

Familiar names Marcel Hug and Hellen Obiri crossed the finish line first for the men's wheelchair race and women's professional division, respectively. A 22-year-old breakout racer, Eden Rainbow-Cooper, won the women's wheelchair division. And Sisay Lemma was victorious in the men's division, leading the pack at a blistering pace early in the race.

Here's a look at how the day unfolded on the route of the 128th Boston Marathon:

While the warm spring day was welcomed by spectators, it was not ideal for those racing into Boston.

Kerin Milesky, who leads disaster and emergency planning at the state's Department of Public Health, said there was a high number of runners visiting the medical tents.

Runners sought medical care for heat-related nausea and cramping. Doctors at the finish line's medical tents said when a wheelchair freed up, it would get filled again right away.

Kristin Molina, of Denver, stopped at a medical tent when she finished the race. She said she got dizzy during the last few miles and her vision blacked out.

"I have no idea why," she said. "I drank water at every stop. Ran a lot slower than I was hoping to the whole time."

Steven Watanabe, of Toronto, said he needed to go to the medical tents to rehydrate from the heat. When asked if he was happy he finished the race, he replied, "happy-ish."

And Jessica Bouchard, of Syracuse, said she started feeling delirious from the heat around mile 22. She said she made it within the qualifying time for next year, "but I don't know if I can do it again. It was painful."

Dr. Pierre d'Hemecourt, one of the marathon's medical directors, said he saw about 25 runners who needed ice baths in the tent where he was working.

The runners were experiencing hyperthermia, heat strokes. We had to "tub a lot of people," he said. "We actually had a constant, ongoing tub — one after the other."

Despite the high need for services, DPH's Milesky said the medical teams were ready.

Milesky says the number of patients needing care is comparable to 2017, when temperatures reached 73 degrees.

Spectators lined the Boston Marathon course to cheer on the athletes Monday.

Stephen Mandile was on "Heartbreak Hill" with his daughters. They come from Uxbridge every year to watch the race.

Mandile is holding a sign that says "I see you, great job! I'm proud of you."

"We know how much effort and work every runner put into, to being here and making this happen," he said. "We want all of them to know that they have fans here, even if they don't know anybody here."

The crowds mean that local businesses along the route have a very busy day. Wellesley Bakery on Washington Street welcomed the marathon crowds. The bakery's owner, Mara Nuon, said today is a special day for the business.

"It's our anniversary — 30 years," Nuon said. "Marathon day has been always special."

Eileen Clancy-Pantano and Julie Kenerson, both of Hull, waited along the route in Wellesley to support their nephew, Patrick Clancy. Clancy ran the marathon in memory of his three children who were killed last year and raising money for Boston Children's Hospital.

Clancy-Pantano and Kenerson stood with a homemade sign decorated with hearts around the names of the three children, Cora, Dawson and Callan and "Go Pat" written in big, blue letters.

Abby Bedard, of West Bridgewater, waited along the barricade in Wellesley to cheer on her sister, Emma. This will be Emma’s first marathon, Bedard said, and her cheering section runs deep.

“It’s our whole family, cousins, uncles, aunts parents, everyone’s here to cheer her on,” said Bedard.

Bedard and her family stood out along the sidelines, all clad blue tee-shirts that read “Let’s Go Emma!!!” featuring a cartoon of the runner drawn by her uncle.

12:10 p.m. Hellen Obiri, of Kenya, wins her second Boston Marathon in a row, with an unofficial time of 2 hours, 22 minutes and 37 seconds.

11:44 a.m. Sisay Lemma, of Ethiopia, wins the men's professional division of the Boston Marathon with a time of 2 hours, 6 minutes and 17 seconds. Mohamed Esa comes in second; Evans Chebet in third.

10:40 a.m. Britain's Eden Rainbow-Cooper, 22, crosses finish line, winning women's wheelchair race — her first major marathon win. Her unofficial finish time was 1 hour, 35 minutes and 11 seconds.

Rainbow-Cooper becomes the first woman from Britain to win the women's wheelchair division.

She raced in Boston for the first time last year and tells WCVB, "it was a really, really tough race."

"I just wanted to come here and finish the race and have fun. I can't believe it."

10:18 a.m. Switzerland's Marcel Hug becomes seven-time Boston Marathon men's wheelchair champ, smashing his own record, despite a crash in Newton.

Hug already had a four-minute lead about 18 miles in when reached the landmark firehouse turn in Newton, where the course heads onto Commonwealth Avenue on its way to Heartbreak Hill. He spilled into the fence, flipping sideways, but quickly restored himself.

He finished in 1 hour, 15 minutes and 33 seconds, breaking his previous record by a minute and 33 seconds.

Hug tells WCVB "as always here in Boston, it was a challenging course," but he said the conditions for him today were "perfect." He described his efforts as "just a race across the clock."

"I love doing races, especially here in Boston" he says. The crowds give off "so much energy. ... Thank you, Boston, I love you."

"Heartbreak Hill" is one of the most difficult parts of the race. It’s the steepest and longest hill  capping off series hills in Newton. Spectators on the sidelines are some of the most enthusiastic, encouraging racers along as they battle the hill.

Laurentia Mei knows the value of Heartbreak Hill cheers. In 2019, her husband, Winston, was sick with food poisoning when running the race. He was thinking of giving up when he saw Mei on the hill.

“We told him, you only have six miles to go. You can do this. You can do this,” said Mei. “So then he went, continued the marathon and he did it.”

Mei is part of a marathon family forged on the Heartbreak Hill sidelines. She met fellow spectator Sterling Crockett on the hill a few years ago. When Crockett ran the New York Marathon last year, Mei was there watching for him at the finish line.

“She gave me a big hug and we took a picture together at the finish line of the New York Marathon. It’s amazing,” said Crockett, who wore a tricorn hat to the race this year in honor of Patriots’ Day.

10 a.m. The first wave of non-elite racers have started the Boston Marathon. Three more waves will start in 25 minute increments.

9:47 a.m. The professional women's division is off and running.

Hellen Obiri, who won the women's medal last year, has returned. The two-time Olympic silver medalist in the 5,000 meters is among the favorites in today's race.

Top Americans include Emma Bates, who finished fifth last year. The 31-year-old former Boston resident stepped in a pothole midway through the Chicago Marathon last fall, tearing a tissue in her foot.

The injury led to a setback that kept her from competing in the Olympic marathon trials in February. So she's back in Boston, a year after she led the pack through Brookline with the crowd chanting her name.

“That was the coolest thing I’ve ever done in my career, that’s for sure,” she said last week. “Being in the lead and setting myself up for the most success that I could have on that day, it was just really special to know that as long as I trust myself, as long as I go after it, that I can do pretty big things.”

Sara Hall, who has reached the podium in two major marathons, joins Bates in a strong American contingent.

9:37 a.m. The professional men's division has left the starting line.

Two-time defending champion Evans Chebet is back as he tries to become the first three-time winner since 2008. The last time that happened was when Robert Kipkoech Cheruiyot won three in a row from 2006 to 2008.

Handcyclists and duos are also on the course now.

9:10 a.m. Both the men's and women's wheelchair divisions are on the course.

Here's a look at the records to beat:

Grand Marshal and former New England Patriots NFL football player Rob Gronkowski will ride along the course route, cheering on the racers and waving at marathon spectators.

Gronkowski, arriving at the finish line just after 10 a.m., tells WCVB that he didn't know what to expect earlier today at the starting line, but he has enjoyed seeing all of the cheering and support for runners from spectators.

He described the vibes along the course as being like "a 26-mile parade" and noted that he did not attempt to spike the winner's trophy because he would have broken it.

Eleven years ago today, three people were killed and hundreds injured in the Boston Marathon bombings.

Gov. Maura Healey, Boston Mayor Michelle Wu and family members of the victims took part in the annual wreath-laying ceremony at a memorial near the finish line on Boylston Street — the location where the bombs went off that day.

Temperatures will quickly rise into the 60s today. Those conditions aren't so ideal for the runners, but will make for a beautiful day for the crowds of spectators. Here's the full forecast.

9:02 a.m. - Men's Wheelchair
9:05 a.m. - Women's Wheelchair
9:30 a.m. - Handcycles & Duos
9:37 a.m. - Professional Men
9:47 a.m. - Professional Women
9:50 a.m. - Para Athletics Division
10 a.m. - Wave 1
10:25 a.m. - Wave 2
10:50 a.m. - Wave 3
11:15 a.m. - Wave 4

It's Patriots' Day in Massachusetts, a state holiday that commemorates the battles of Lexington, Concord and Menotomy that began the Revolutionary War. Here's a look at what's open and closed today.

WBUR's Martha Bebinger, Simón Rios, Willoughby Mariano, Sydney Ko and Katie Cole contributed to this post. The audio atop this story is a conversation on WBUR's All Things Considered between host Lisa Mullins and reporter Alex Ashlock.