Wednesday's high at BWI Marshall Airport was 90 degrees, starting a stretch of potentially seven days or more with temperatures above the 90-degree mark, if forecasts hold up. It would take a much longer stretch to set a record, however.
The National Weather Service has placed central and southern Maryland and the Eastern Shore under a heat advisory 11 a.m. to 8 p.m. Friday, canceling an earlier excessive heat watch. The advisory cautions of heat indices up to 105 degrees.
The weather service is calling for highs to approach 100 degrees for the next five days, through Tuesday at least. Thursday's high is predicted in the mid-90s.
Baltimore's health department on Thursday morning issued a "Code Red" heat alert for Friday through Sunday, opening city cooling centers. Anne Arundel County plans to open cooling centers Friday through Monday.
A nine-day stretch in the 90s would rank in the top 40 longest stretches of 90-degree weather for Baltimore, according to weather service data. The longest stretch on record was 25 days ending Aug. 5, 1995.
A stretch from summer 2011 was nearly that long -- highs were in the 90s and 100s for 17 days straight through Aug. 2 of last year. There were handful of other stretches lasting 5 days or fewer.
The previous summer, highs hovered in the 90s and 100s for 11 days ending July 25.
The weather service's forecast only extends out six days, but AccuWeather, which recently debuted a 25-day forecast, is calling for highs in the 90s through July 9. That would make for a stretch of 13 days above 90.