By Sarah Wroblewski

BOSTON (CBS) — It was only two weekends ago that the discussion was the dreary conditions as afternoon highs were stuck in the 40s and 50s. Worcester set new record cold high temperature records, staying in the 40s all weekend. It even snowed at Stratton Mountain in Vermont on Saturday morning.

Well this past weekend, it’s like someone flipped the switch to summer.

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SATURDAY

Well, the weekend came in HOT. Boston hit 91 degrees Saturday afternoon, under mostly sunny skies. What a difference in temperatures from inland locations with low 90s, and to the Cape and Islands where highs were in the 70s!

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SUNDAY

The heat continued on Sunday. Boston hit 94 degrees, making it the hottest day of the year so far. Humidity ticked up slightly, and that will be a trend into the work week.

A Heat Advisory is in effect through Monday evening. With highs in the mid-90s, plus combining the humidity, heat index values to soar to the upper 90s.

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HEAT WAVE ON THE HORIZON 

In order a heat wave to be official, a city must have three straight days of 90° or higher temperatures. Saturday likely marked the first day of the season’s first heat wave. This very hot stretch is likely to continue into Tuesday and possibly Wednesday.

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Keep in mind, there is the potential of heat related issues to those at risk, and those doing higher levels of outdoor strenuous activity. If you are outside, wear light colored clothing, try to find ample shade, take breaks and drink plenty of water.

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Boston now has four 90°+ days for the season, slightly ahead of the year-to-date average of one day thus far.

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Sarah Wroblewski