Heat Wave Watch

BOSTON (CBS) - It hasn't happened in over two years in Boston. The odds favor it will happen Monday.

What is it?

It's a heat wave which consists of 3 consecutive days at 90 degrees or higher.

It briefly struck 91 on Saturday and 90 yesterday so today's prediction of 90 will satisfy the criteria. Boston's official weather station is located at Logan Airport. The proximity to the ocean plays a huge roll in the weather records for the city. It is the reason that Boston has not experienced a heat wave this summer or last summer on a few occasions when inland locations have. Boston's famous east wind will cool the coastline and that may happen to prevent 90 degrees today but the wind may not flip to an onshore breeze until that 90 is attained by noon.

Boston's last heat wave was a scorcher lasting a whopping 7 days in July of 2013. The record book reveals several heat waves lasting 8 days over the last 140 years. The longest heat wave of 9 days occurred on July 3-11, 1912. One of the longest late-season heat waves took place on August 9-15, 1988. That was a summer following a strong maturing El Nino in the late fall and winter of 1987-88. In most cases, summers following El Ninos transitioning toward La Ninas yield torrid weather. Again, the preliminary somewhat speculative long-range prediction for next summer is torrid weather with the potential of near 25 days at 90 or higher.

So after this weekend, the count stands at 8 days at 90 or higher which matches last year's total. Note the 24 days in 2010 which was also coming off a moderate El Nino in 2009 into early 2010. There were 30 days at 90 or higher in 1983 following the very strong El Nino of 1982 into 1983! The average number is 14. I am predicting 4 more this season which is close to my projection of 10-12 issued earlier this spring.

The upper air pattern of steering currents (courtesy: WeatherBell) favors warmer than average weather well into September. That doesn't necessarily mean a lot of days at 90 or higher. There were 3 days over 90 in the first week of September last year. Heat waves are unlikely in September as records show only 3 since 1872!

The second half of this week will be cooler but still quite humid with showers most likely on Friday. After that, high pressure building over the Northeast and offshore will provide daily breezes in from the ocean.

Make it a great week!

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• Heat Wave