The Bottom Line
Here's a fun factoid: Historically, approximately 95% of New Jersey heat waves occur after June 7th. (That is, 265 of 279 heat waves at Newark since 1931.) That shows just how unseasonable - but not unheard of - our current stretch of hot, humid weather is.
Temperatures will run 10 to 15 degrees above normal for three more days: Monday, Tuesday, and Wednesday. After a weekend of hazy sunshine and bone-dry weather, we will have to add some clouds and thunderstorms to the mix.
Thursday looks like our big cooldown day. And the difference between "hot" and "not" will be stark. By next weekend, we should settle into more seasonable conditions for mid June.
Following a hot, humid, summery weekend, I have no doubt we'll make it an "official" heat wave Monday - that is three days in a row of 90+ degree temperatures.
I always say that the "worst" part of a heat wave is when temperatures don't cool down at night. Usually the benchmark is 70 degrees for warm vs. comfortable low temps. Temperatures are primarily in the 60s to start your Monday - not bad.
Highs will soar into the lower 90s across most of New Jersey - similar to Sunday. Of course, the Jersey Shore will be the cool spot in the state, closer to 80 degrees (especially on barrier islands.)
The combination of heat and humidity is going to feel especially suffocating in urban areas, as the heat index (the "feels like" temperature) potentially exceeds 97 degrees. A Heat Advisory is posted until 8 p.m. for Mercer, northwestern Burlington, Camden, and Gloucester counties.
While we will start the day with hazy sunshine, substantial cloud cover will build Monday afternoon.
In addition, there's a good chance we see a popup thunderstorm somewhere in the state too. Very isolated, but capable of producing a brief downpour and some gusty winds. According to forecast models, the best chance of such a storm would be in northern New Jersey.
I'll keep a shower in the forecast for Monday night, with mostly cloudy skies and muggy conditions. Low temperatures will only fall into the lower 70s by Tuesday morning.
Probably the best chance of showers and thunderstorms will develop Tuesday, from midday to early evening. (About lunchtime to dinnertime.) Odds are pretty good that most of New Jersey will see some raindrops. And those storms could push out some heavier rain and wind too.
Because of the rain chance and a mix of sun and clouds, temperatures will cool slightly. Highs will reach the upper 80s to around 90 degrees. While part of NJ may fall out of "heat wave" territory, it's still going to be unseasonably warm and uncomfortably humid.
About the same as Tuesday, although fewer models paint a stormy scenario for NJ at this point. Mostly cloudy, with scattered thunderstorms possible. For one more day, highs will once again push into the upper 80s to around 90 degrees.
The big cooldown day. As a cold front passes through New Jersey, it will turn dramatically cooler and less humid. Our latest forecast calls for highs in the mid 70s, with clouds and a stiff east-northeast breeze.
I do have some hesitation about the timing and extent of that cooldown. I'm not sure if we can truly call this a "backdoor" front - but it is unusual, because it will affect NJ from due north to due south. (Regular fronts sweep from west to east, while backdoor fronts show more of a northeast to southwest progression.) In any case, we've had several cases this spring of backdoor cold fronts in the forecast completely washing out before arriving. It's a non-traditional end to a rather unusual heat wave - that's why confidence is low and minds are open for now.
Friday & Beyond
Both the GFS and Euro models show a batch of steady-ish rain clipping New Jersey around early Friday morning. And then clouds and surprisingly cool temperatures will end the workweek, as we only top out in the 60s. (A full 25 degrees cooler than earlier in the week, by the way.)
It's a little too far out to fully nail down the weekend forecast yet, but I like what I see. Partly sunny and 75 to 80 degrees? That's right on the normal for mid June, with only about a week to go until the Summer Solstice.