SAN DIEGO - Kirsten Allan and Lindsay Benster share a sisterhood.

Both ran track and cross country at USD under head coach Will Guarino, Allan until her 2012 graduation as a business administration major, Benster until 2017, majoring in behavioral neuroscience.

While the women never competed on the same team, Allan coached with Guarino for three years, taking Benster under her wing.

“You talk about grit, I think she’s the definition of grit,” Allan, 27, said of her protégé.

Said Benster, 24, of Allan, “She’s one of my biggest support systems ever. Always calling, always texting. One of the most supportive people I know.”

On April 16, more than 3,000 miles from the Alcala Park campus where they met and bonded, Allan and Benster shared a day that was equal parts miserable and momentous. The two Toreros were among nearly 30,000 runners who braved some of the most brutal conditions in the 122-year history of the Boston Marathon.

Allan completed her fifth Boston Marathon, while Benster finished her first.

Battling temperatures in the 30s, a head wind that pushed to 32 mph and constant rain that one time turned to sleet, Allan and Benster completed the 26.2-mile odyssey from Hopkinton to downtown Boston.

Completing her fifth Boston Marathon, Allan finished in 3 hours, 14 seconds to place in the top 100 among all women (78th) and finish 1,844th overall. Running the race for the first time, Benster finished in 3 hours, 11 minutes, 12 seconds to finish 315th among all women and 3,556th overall.

Describing the rain, Allan said, “Heavy drops that were almost like water balloons coming down. The sleet felt like marbles pegging you, a little bit like needles.”

For Benster, at one stage the wind howled, coupled with the freezing rain. She turned to a runner next to her and both smiled, the unspoken message being, “It can’t get any harder than that.”

Allan’s highlight at USD came not at a long distance but at 800 meters on the track, where she ran a school-record 2 minutes, 15.94 seconds, which has since been broken. Guarino, though, told Allan her future would be at longer distances.

After graduating in 2012, she ran a half marathon in November, then the San Diego Rock ‘n’ Roll Marathon in June 2013. Allan’s finishing time of 2:56:39 qualified her for the 2014 Boston Marathon.

Allan has raced Boston every year since. Her first Boston race came one year after the Boston Marathon bombings when three people were killed and hundreds injured.

“When I showed up and felt the banning together of an entire city, it was something pretty incredible,” said Allan.

Boston is the world’s most famous and oldest annual marathon. It was first held in 1897, inspired by the revival of the marathon for the 1896 Summer Olympics in Athens, Greece, and has been staged every year since.

It is held on the third Monday of April on Patriots Day, a Massachusetts holiday. Because of the race’s history and the holiday, an estimated 500,000 spectators typically spill onto the course, which spans eight towns and cities.

“People have this tradition of going out, cheering on runners, whether they’re a toddler or in their 80s,” said Allan. “The first year, I experienced the insane community camaraderie. They won’t let athletes quit. In hot conditions, people rush over to help athletes.

“(After the race) you walk around wearing your medal, people want to shake your hand, congratulate you, call you a hero.”

It’s that support and the Boston Marathon’s history (the screaming Wellesley co-eds, Heartbreak Hill, having to run a fast enough time at another race to qualify) that has kept Allan returning to Boston. When she coached at USD, she earned runners’ respect because her training enabled her to push athletes in workouts. She shared Boston stories.

Gradually, it became a tradition among USD women cross country athletes, wanting to celebrate their graduation by running a marathon.

Benster continued a USD tradition of running a marathon after graduation.

“I always wanted to run one with her,” said Benster. “I figured I had to qualify for Boston in order to do so.”

Benster qualified last June at a Seattle marathon.

Allan lives in Gunnison, Colo., where she works as a physical therapist. Benster remains in San Diego, doing research at UCSD in the department of psychiatry. They kept in touch leading up to the Boston Marathon, trading training tales.

The day before the marathon, they met in downtown Boston. Benster wanted to jog a portion of the course. They ran for 30 minutes, heading toward the Boylston Street finish, observing a USD tradition, making sure they did not cross the finish line.

“That’s bad luck,” said Allan.

Allan shared race-day tips for her protégé: the first 10 miles are a net downhill, so despite how good Benster might feel, be conservative; a breakdown of the race’s famous hills; and, “Have fun,” said Allan. “Boston’s a 26.2-mile celebration of all the hard work you put in.”

Race day dawned cold and wet and windy, miserable for lithe runners with little body fat to protect them.

“Brutal conditions,” said Benster.

Her body was cold at the start.

“You’ll warm up by Mile 7 or 8,” Benster told herself.

Her body never cooperated.

“I told my body it’s not going to get warm,” Benster recalled. “I had to make peace with that.”

By Mile 24, Allan said, “I couldn’t really feel my legs.”

Neither runner gave serious consideration to quitting.

“I don’t think quitting is in my nature,” said Allan.

She is hardened, in part, by the legacy of her mother beating lymphoma when Allan was a toddler.

Both runners said Guarino also instilled in them a fierce competitive spirit.

“If you start a workout, you finish that,” said Benster. “Races are no different.”

Allan and Benster started one corral and 25 minutes apart, so they did not run together. Shortly after crossing the finish line, Allan texted Benster’s mother, asking for an update. When Benster finished, she was shivering. She headed to a nearby hotel where the family was staying and buried herself in a long, hot shower.

Her father delivered hot chocolate. She huddled herself in layers.

Guarino sent the women a text message: “Was tracking you this morning. Congrats. Proud of you both.”

The next morning, Allan and Benster met for coffee near the finish line. Both had flights home that night. They sipped, and talked for 30 minutes, trading yarns about the race’s miserable conditions.

On race day, both wore USD racing shirts that featured the San Diego script across the front.

“San Diegans are running in this weather?” a spectator marveled to Allan.

Of her race-day attire, Allan said, “I always have to represent USD. That’s where I formed my running habits. I am who I am today because of that program.”

Said Guarino days later regarding the toughness the women exhibited on a miserable Boston spring day, “It’s just an attribute of their personal character. It’s something I saw in them during the recruiting process.

“They are wonderful, bright women. Really, very powerful women, and they show it through their running.”