HEAT IS GROWING CONCERN FOR OFFICIALS

THE BOSTON GLOBE

BOSTON — The Run for the Hoses. The Duel in the Sun. The Inferno.

As the prospect of 80-degree temperatures looms over Monday’s Boston Marathon, race organizers are hoping the heat will forge a classic contest to rank among the legends of the event’s 116-year history even as they prepare for a potential medical crisis if runners wilt under the scorching sun.

The forecast forced organizers to offer a largely unprecedented deferment to the entire field of 27,000 that had spent the last year qualifying, registering and training for what is often a once-in-a-lifetime experience.

‘‘We’re asking runners who haven’t run previously to think about tomorrow and maybe coming back next year,’’ Boston Mayor Tom Menino told the attendees at the traditional pre-race pasta dinner on City Hall Plaza on Sunday night. ‘‘We don’t want have any accidents out there, or anybody overtaken by the heat.’’

The Boston Athletic Association also offered a deferment in 2010, when the Icelandic volcano eruption stalled air traffic in Europe and prevented about 300 runners from getting to Boston. There is no way of knowing how many will take them up on the offer this year until Monday morning, when the number of no-shows is calculated.

The Boston Athletic Association urged Sunday that “only the fittest runners” should consider participating in the Boston Marathon as temperatures are expected to surge.

B.A.A. co-medical director Pierre d’Hemecourt warned runners with underlying medical issues, such as a cough or a cold or a recent stomach virus that left them dehydrated: ‘‘Please don’t run the marathon on Monday.’’ Those who have not run a full marathon before, or who have not run in the heat, should also sit this one out, race organizers said.

‘‘Only the fittest runners should consider running. The risks that you’ll see tomorrow are simply greater than normal,’’ B.A.A. executive director Tom Grilk said, advising runners who do line up at the start to slow their pace and focus on finishing rather than a fast time. ‘‘You should adopt the attitude that this is not a race; it is an experience.’’

One year after cool temperatures and a significant tailwind — perfect running weather — helped Geoffrey Mutai finish in 2 hours, 3 minutes, 2 seconds for the fastest marathon ever, the heat has elite runners preparing for a slower pace and the recreational runners trying to figure out how to finish at all.

Forecasts call for 73 degrees at the 10 a.m. start in Hopkinton, 80 degrees at the halfway point in Wellesley by 11 a.m. and 82 degrees at the Back Bay finish line at noon. For the recreational runners expecting to be out on the course later that afternoon, temperatures are expected to peak at 84 by 3 p.m.

Although Mutai said he has never run a hot marathon, fellow Kenyan and defending women’s champion Caroline Kilel said she was used to training in warm weather. But Kilel said the typical conditions were more like 73 degrees — hot for a marathoner, but not quite what’s expected on Monday.

‘‘The heat affects everybody. Nobody runs fast in the heat. Nobody benefits from the heat,’’ 1968 winner Amby Burfoot said this weekend as the weather became the dominant topic of conversation. ‘‘If anyone’s been training in Miami, that would be great for them.’’

The Boston Marathon has had its share of hot weather, with the thermometer hitting 97 degrees during the 1909 race that came to be known as ‘‘The Inferno’’ and the 1976 ‘‘Run for the Hoses’’ that started in 100-degree heat and finished with spectators sprinkling winner Jack Fultz with garden hoses to cool him down.

‘‘It’s just the worst thing a marathoner can face,’’ said Burfoot, who ran with Fultz for half of the ‘76 race before fading in the heat. ‘‘I hate that the marathon is such a crapshoot. You train for 4-6 months, and the only thing that matters is the weather.’’

There were only 2,188 entrants in the ‘76 race, and still just 7,647 six years later when Alberto Salazar won the ‘‘Duel in the Sun’’ against Dick Beardsley.

This year’s field of 27,000 presents organizers with a new challenge.

Because of qualifying requirements, most of the field will have run a previous marathon in a time that can be as low as 3 hours, 5 minutes for men aged 18-34. But the times go up — to 5:25 for an 80-year-old woman — and several thousand other runners receive entries with no requirement to have run a marathon by raising money for charity.

And even those who have run good times in the past could be caught unprepared by the hot weather.

The last on-course death of a Boston Marathon participant was in 2002, but the Chicago Marathon stopped its 2007 race after 3 1/2 hours when a runner died after temperatures climbed to 88 degrees.

The B.A.A. renewed warnings on Sunday night to drink enough — but not too much — water, and to recognize the symptoms of heat stroke: confusion, headaches, nausea, vomiting and excessive fatigue.

Race director Dave McGillivray said organizers will have double the water on the course, along with more ice and more emergency staff to deal with problems from the heat. Emergency rooms along the course are also preparing for a potential influx of heat-related problems, and Menino said the city will also boost the police presence.

Also a concern are the hundreds of thousands of spectators who line the 26.2-mile course.

‘‘The message out there is bring your own stuff,’’ Grilk said. ‘‘We have a lot of water on the course, but we need to conserve it for the runners.’’