Monday's 130th Boston Marathon will start in Hopkinton in the low 30s and is projected to finish in Boston in the mid-40s, with a 10- to 25-mph northwesterly wind creating a course tailwind and a spectator-line crosswind. [1] WMUR's forecast Thursday said Monday's high could set the coldest high in Boston Marathon history, exceeding 2009's 48°F. [2] The paper's Sunday security-posture piece on the 130th running named the heightened-threat environment. Monday's separate story is the temperature.

For the elite field, this is the best weather of the last decade. A sub-2:06 men's time becomes plausible; a sub-2:18 women's time, likelier. Cold distance running is the textbook thermodynamic advantage — heat loss scales with the race — and the Globe's April 15 review of the coldest Boston Marathons noted that the 1910 and 2018 standouts both produced course-record-adjacent performances despite their other miseries. [3] The tailwind out of the west is exactly what the marathon was paced around when Kathrine Switzer first wore a bib in 1967 and it is exactly what Evans Chebet had last year when the wind was not.

For the 22 runners aged 80 and older, and for the 30,000 total runners plus spectators lining 26.2 miles of road, the cold is hazard. Boston's EMS has requested additional warming stations at the halfway point in Wellesley and at Heartbreak Hill. [1] Michael Holick, 80, starting his third consecutive Boston while being treated for stage III prostate cancer, is the named test case. [3] The cold-as-aid-to-elites-and-hazard-to-elderly frame is the paper's Monday fact. One race. Two physics. The finish time will be posted by Tuesday's edition. The cold's cost is a number the hospitals will still be counting on Wednesday.

-- NORA WHITFIELD, Chicago