The high in Portland reached 91 degrees Sunday, about 15 degrees above the long-term average and the second time we’ve been at 90 degrees or hotter this year. You might have already forgotten, but we had our first run into the 90s in the middle of May when some inland areas saw two days of 90-degree weather.

Today’s temperatures will easily reach the 90s inland and for some coastal towns, with a high likelihood of eclipsing Sunday’s temperatures by a degree or two.

Temperatures this morning were already well into the 80s to near 90

Heat and humidity are most often brought to New England by way of a Bermuda high pressure system off the southeast coast. These weather systems act as heat pumps, throwing hot, humid and often poor-quality air into much of New England.

High pressure of the southeast coast brings warm and humid weather to Maine

There is an air quality alert again today along the coastline. This means if you are someone who suffers from respiratory issues you shouldn’t exert yourself too much. Even healthy individuals can feel the effects of the poor air as it makes it just a bit harder to breathe, especially when exercising.

In addition to the heat, the air isn’t very clean to start this week.

Tomorrow a cold front will start moving south from eastern Canada and Maine. This will put an end to the heat and humidity for the rest of the week. If Portland reaches 90 before the front passes Tuesday (and we hit 90 today), it would be an official heat wave. But I think the chances are only 1 in 10 that the Jetport does hit 90 Tuesday.

Cooler air will push south Tuesday night and early Wednesday. The loop below shows the falling temperatures throughout Tuesday night, setting us up for a much more comfortable Wednesday with low humidity.

Cooler air arrives later Tuesday as a cold front passes.

I don’t see much in the way of rain despite the transition to cooler air. If you’ve shut off your irrigation system, as I have, it’s probably time to flip the switch back to on. Also, don’t forget to water those container plants. This heat dries them out quickly.

The weather may turn a bit damp heading into the weekend, but the details on any shower activity will need to wait a few days. I don’t see any more chances of heat waves for a while.