It’s been “hot and humid” the past few days, but other than one day back in May (still spring), Portland has yet to reach the 90 degree mark this summer. Inland areas like Sanford, Fryeburg and Bridgton have all been much warmer than the coast and this trend will continue much of this week.

Heat and Humidity
In this part of the country, 90 degree weather conjures up thoughts of a heat wave and for many the number represents when it’s just too hot. The funny thing is it can actually feel more uncomfortable at temperatures under 90 than it can with those above because of the humidity. Check out the chart below from which you can calculate the heat index. If it was 90 degrees and the dew point was under 60 then it only feels like 90, but at 84 with a dew point of 74 degrees it feels a degree warmer.

Heat waves are defined as 3 or more days of 90 degree weather or higher. The official records for Portland are kept at the International Jetport which does have water around much of it. Therefore, the number of 90 degree days and heat waves is lower than what most of you experience where you live. A feeble sea breeze, even a few miles per hour, can keep the airport from reaching 90, while it’s 91 or 92 in the North Deering section of the city or out near Westbrook. This fact can make heat wave headlines very misleading.

No Heat Waves
By the way, the last heat wave in Portland was the one from July 21st to July 23rd 2011. The 22nd was also the last time Portland reached 100 degrees and the first time it had happened in 35 years.

The Bermuda high pressure of the southeast coast of the United States is going to act like a heat pump much of this week and bring humid and hot air north. There will be a break in the core of the heat on Thursday, but not before many areas will have experienced five ninety degree days.

This period of the summer will end up as the hottest and most humid this year. Most of the summer we haven’t seen an upper level pattern like the one we have this week. This prolonged period of humidity is going to make it quite difficult to sleep for the foreseeable future although we may get used to it as the week goes along.

If you are on vacation this week it does look wonderful for all outdoor beach activities although if you have more strenuous activities you might be doing I would try to get them done in the morning before the heat is at its worse.

I don’t see any widespread rain or thunderstorms in the forecast although there could be some shower activity in isolated pockets in the mountains on Tuesday and again late in the week or early next weekend. The 90s will break by Wednesday or Thursday, but the humidity may remain present for much of the week.

Tropical Threats
The global tropical picture remains quite active, but the Atlantic Basin, which is where any storms that affect us would come from, has been quiet. The outlook from the National Hurricane Center is predicting one area that might become organized during the week, but overall it’s still quiet in the areas which would mean problems if they became active. The peak of hurricane season won’t arrive until September.

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