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."
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