(CNN) -- Before they can bask in glory, Boston Marathon runners on Monday will first bake in abnormally high temperatures -- so warm, in fact, that race organizers are taking several steps to warn participants and allow those concerned about the heat to instead run next year.
The race, which began in 1897 and bills itself as the world's oldest annually contested marathon, is typically held in relatively cool weather. The average temperature for an April day in Boston is 47 degrees -- with a usual high of 56 and low typically of 40 degrees -- according to the city and National Weather Service.
Still, with its rolling hills, the Hopkinton-to-Boston course is often considered among the nation's most grueling marathons even in ideal racing conditions, which usually imply temperatures in this same 40s and 50s range, light winds and cloudy skies.
But that's far from what runners will encounter this year. Monday's forecast from the National Weather Service calls for sunny skies and a high temperature of 88 degrees, with sustained winds blowing out of the southwest at between 7 and 15 mph.
For this reason, the Boston Athletic Association has taken the unusual step of urging even very fit participants to "run at a slower pace" and "frequently take breaks."
"This will not be a day to run a personal best," the race organizer said in its online statement. "If you choose to run, run safely above all else. Speed can kill."
The BAA also recommended that those who are "not highly fit" or who have "any underlying medical conditions" not run, even if they have a much sought after bib number. Besides elite runners, people can get a spot in the Boston Marathon by qualifying based on their time in another marathon or getting a position as part of an effort to raise funds for charity.
To that end, the association announced last week that any official entrants in the 2012 race can defer and instead run in the 2013 Boston Marathon. Those taking up this option don't have their entry fee refunded but simply reserve a spot in next year's race.
The hot weather forecast early this week is exceptional for Boston, though it's in line with the trend that has been building over the first few months of this year.
The average temperature in Boston from January through March was 39.4 degrees, the warmest recorded for that time stretch, the weather service reports.
Two runners died while participating in November's Philadelphia Marathon, the race's executive Melanie Johnson said.
But weather there was not believed to be a factor, as there were cool temperatures, light winds and most cloudy skies throughout the race.
That same month, a 30-year-old male runner at the New York City Marathon collapsed with cardiac arrest and was transported to Mount Sinai Hospital.