Heat Wave Versus a Warm Stretch – Breaking Down the Differences and Looking at Our Records

A heat wave is three days in a row (or more) of 90 degrees or higher, but we also track streaks of 80 degrees or higher

NBC10 Boston

Summertime means some hot stretches from time to time.  Our normal high temperature for this time of the year in Boston is 82 degrees, with an average low of 67.  This month has been warmer than normal overall and we even had one heat wave that really bumped up our average for this July. 

As we watch for another hot stretch ahead for the city, we may not actually be able to call it a heat wave.  A heat wave is three days in a row (or more) of 90 degrees or higher.  An onshore wind on Wednesday may keep us away from that 90- degree mark, breaking the 90-degree streak in half.  So lowering the threshold for warm stretches, we looked at the longest streak for 80 or higher in Boston.

The top spot is 24 days with 80 or higher, ending on July 11, 1953.

The second is 22 days ending on July 21, 1876.

The third is 21days ending on July 18, 2012.

Fourth is 20 days ending on July 17, 1872.

It's a tie for fifth - each 19 days ending on August 10, 2018 ,and July 24, 1993.

It's also a tie for seventh - 18 days ending on August 5, 1994, and August 6, 1979

Ninth is 17 days ending on August 20, 2016.

And 10th is 16 days ending July 23, 1983.

For comparison, our longest heat wave in Boston was nine days with an ending date of July 11, 1912.

It’s worth noting that the stretch of 17 days in 2016 was actually during a bad drought -- one even worse than this year’s drought (so far).  By October 4 of that year, drought conditions had escalated to “extreme” in Boston.

This year we have had 15 days (including today) of 80 degrees or higher in a row in Boston Starting on July 15. 

We have more 80s forecast for the weekend, and then go to the 90s next week. 

The potential is there for a streak of at least 25 days as we have 80 or higher in for the next 10 days.  And this would mean a new record.  Stay tuned!

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