A summer weather pattern has set up early this year, leaving us at the mercy of high pressure off the coast

During the course of the summer our weather is primarily controlled by a big area of high pressure off the coast. At times this high is particularly strong and it brings us a lot of heat and humidity. Occasionally it weakens allowing cooler air to come in from the north with a smattering of showers in between. That’s pretty much how things work from June through August.

High pressure in the Atlantic keeps the eastern United States warm and humid most of the summer.NASA

This year, this pattern has set up notably early. As the climate continues to change, summer weather arriving early may become the norm. Early morning risers this week must have noticed we’ve gone from being in the 40s at dawn to the 50s and even near 60. Each day the sun works on the air mass and warms it just a little bit. Temperatures reached the mid-80s yesterday and the 84 degree high temperature at Logan airport was the warmest since Sept. 28, 2020.

Here’s more details on the forecast for the next few days:

It won’t matter where you are today, it’s going to be a beautiful day. The differences will come from being in places like Provincetown compared to westward locations like Acton or Franklin. These inland locations along the I-495 belt will easily reach and exceed 80 degrees this afternoon. From the water’s edge out to the Route 128 belt, temperatures will stay in the 70s today and in these areas there will likely be a pullback of the warmth this afternoon as the seabreeze penetrates further inland.

Cooler air moves in from the ocean during the afternoon in this model's forecast.Weatherbell

I think we have a similar setup for tomorrow with cooler marine air along the coastal plain, but midsummer warmth well inland. If you’re not a fan of the early summer temperatures, at least the humidity is low. Early warmth can feel more intense this time of year because of the strength of the sun. We are now just about four weeks away from peak solar heating and the gains we will make until then are fairly negligible.

The path of the summer sun is much longer and higher across the sky.NOAA

That high pressure area I wrote about will begin to break down as we head into the weekend. This process is usually slower than predicted so I think it stays warm until Sunday night. There will be some additional humidity over the weekend, increasing the chance of widely scattered showers — but it’s more likely that we miss all of them and it stays abnormally dry. The lack of rain will make the pine pollen literally stick around, keeping the pollen count really high.