BOSTON (CBS) – The heat is on. Temperatures on Friday rose above 90 in the afternoon, meaning the heatwave has officially begun.

A reminder that to attain an official heatwave, you must hit 90 or higher for 3 straight days. The last official heatwave in Boston was last August 27-30. That was our second of the year, following the June 29-July 1 heatwave. You can lock this one up, there is no doubt that July 19-21 will go in the record books as the first heatwave of 2019.

The run for 100:

Hitting 100 in Boston is truly a remarkable occasion.

It has only happened 25 times in the nearly 150 years of record keeping in Boston, about once every 6 years on average.

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I guess you could say we are due. The last time Boston hit or surpassed 100 degrees was 8 years ago, July 22, 2011 (103).

If we hit 100 on Saturday it would also be a record for the date, surpassing the 99 degree mark set in 1991.

Sunday’s record is a bit harder to reach (102 degrees in 1977).

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Warmest weekend evah?

That may be a stretch, but this weekend is nearly certain to approach the top 5 warmest weekends ever recorded in Boston. Measuring by average temperature (a combination of the high and low for the day), the warmest weekend ever in Boston was back in July of 1991, the average temperature for that weekend was 89.3 degrees. That may be tough to accomplish, but we certainly have a shot at reaching number 5 on the list, August of 1948 with a two day average of 86.5 degrees.

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Even the nights are hot…

We will also challenge some record high minimum temperatures this weekend. Temperatures on Saturday in Boston did not fall below 80, which tied the record for the date. Another chance of a record high low will come on Sunday morning. Sleeping will NOT be comfy.

It’s not the heat, it’s the humidity…

Heatwave or not, any way you slice it, this weekend is gonna be oppressively hot and humid. The National Weather Service has issued an “excessive heat warning” for most of southern New England on Saturday, expecting heat indicies near 110 (the feels-like temperature when you combine the temperature and humidity). 100 and dry is one thing, but 100 and humid is a whole different beast.

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The more humid it is, the more water there is in the air…and that makes it hard for our bodies to cool down. When our body temperature rises, sweat is released from our skin.

That water evaporates, drawing heat from our body thereby cooling us down. When that water cannot readily evaporate (because the air is too moist and filled with water already), it is harder for our body to cool itself down.

(WBZ-TV)

This leads to a serious risk for heat related illnesses (heat exhaustion and heat stroke). If you must be outside for any extended period of time this weekend, you should seek as much shade as possible, stay hydrated and avoid strenuous activity. And please don’t forget to check your pets!

Record run…

In case you are keeping score at home, some numbers to keep an eye on this weekend…

Saturday:

Record high: 99 Current forecast: 98
Record high minimum: 80 Observed Low: 80

Sunday:

Record high: 102 Current forecast: 99
Record high minimum: 81 Current forecast: 79

Stay cool!

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