As relentless heat roasts the western, central and southern United States, the Northeast has largely escaped the sweltering soup this summer. It joins the Pacific Northwest among the lucky regions with a limited need to run the air-conditioner in recent weeks.

From Virginia to Maine, temperatures have been remarkably normal – or close to average. That’s a major victory for a region that has seen rapid warming from human-caused climate change and endured a siege of scorching summers in recent years.

The relief has been palpable from Richmond to Boston.

Richmond, a city known for its swamplike mugginess, saw its least humid June in a decade, according to Sean Sublette, chief meteorologist for the Richmond-Times Dispatch. As dry air sheds heat more quickly than moist air at night, the city also registered its coolest low temperatures in June since 2012.

Washington has likewise missed out on its typical share of scorching days and saunalike nights. On Independence Day, the dew point – a measure of humidity – dropped to 49 degrees, a shockingly low value. Average dew points in July are in the upper 60s.

Any dew points under 60 are refreshing in the Mid-Atlantic at this time of year. In late June, they even dipped into the 30s in Washington, which is practically unheard of.

The nation’s capital has yet to see a heat wave this summer, defined as three days in a row with 90-degree weather. It has recorded just 12 90-degree days so far, six fewer than normal. The last summer with this few to date was 2009, and it had only two heat waves, the first not occurring until August.

The number of 90-degree days is also down in New York and Boston.

New York has had seven 90-degrees – a near-normal number, but Boston has seen only two, which is three fewer than typical.

“[S]ince mid May it’s been nothing but great almost every day,” tweeted Eric Fisher, chief meteorologist for Boston television affiliate WBZ.

The reprieve from the heat can be traced to the shape of the jet stream, which is the high-altitude wind current that divides hot and cold air and is the superhighway for storms.

While the jet stream has bulged northward over the western and central United States, it has taken a dip in the eastern United States, frequently running through the Mid-Atlantic. That has allowed a somewhat regular stream of dry, cool Canadian air to funnel into the Northeast.

The jet stream has also curled around the Pacific Northwest, which has also seen a relatively mild summer – a welcome break after last year’s historic heat wave.

But for areas south of the jet stream – in the central and southern United States – the heat has been punishing and persistent. Texas has been hit particularly hard.

The nice weather in the Northeast has come at a cost, though. As it has remained north of the storm track, very little precipitation has fallen. Moderate to severe drought has developed from eastern Connecticut through southern Maine.

The Mid-Atlantic, meanwhile, has been in a prime position for heavy rainstorms – situated right along the jet stream’s path. Both Washington and Richmond have been slammed by intense storms in the past several weeks. The Washington region has also seen multiple instances of flooding, as have many locations to its southwest.

While much of the Mid-Atlantic and Northeast have avoided long spells of excessive heat and temperatures have hovered near the recent 30-year average, its temperatures have still been elevated looking over a longer horizon.

In records going back about 125 to 150 years, the average summer temperatures so far in Richmond, Washington, New York and Boston all rank among the top 45 warmest. In other words, this summer’s weather would have been abnormally warm a century ago, even if it’s considered normal now – a testament to the influence of human-caused climate change.

Although the Mid-Atlantic and the Northeast have managed to avoid an onslaught of heat, computer models are signaling a warming trend in the upcoming week.

Richmond and Washington are forecast to see highs in the 90s, while New York and Boston are near 90.

Rather than taking a dip over the Northeast, the jet stream is predicted to flatten out and jog slightly northward – shifting enough to allow some heat to swell over the region.

As we head into August, it’s not clear whether the jet will shift farther north, causing the Northeast to bake, or whether it will revert to taking a dip.

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