A "marathon" heat wave is expected to last through the week, with temperatures reaching 84 degrees or above each day, marking the longest stretch of this kind of hot weather in any month in San Francisco since 2007. The forecast highs are expected to be in the top ten hottest days ever recorded in March in the city starting today. If the high hits 88 degrees on Tuesday, which would break the record for being the hottest March day ever recorded here, it would be the highest March day in the history of San Francisco. The National Weather Service has issued a warning that people should be careful outside due to the long duration of this heat event and increase susceptibility to heat related illnesses.