BOS set a daily record. Maximum daytime heating today boosted temperatures 4 degrees in less than an hour in Boston to set a new daily high temperature record for June 19 — 98 degrees, breaking the previous record of 96 degrees that was set in 1923. Today marks the hottest day in Boston since Aug. 9, 2022, according to National Weather Service records. The heat index value also reached a staggering 107 degrees, as well.