Goodbye summer weather: Cooldown and rain arrives this weekend for NJ

The Bottom Line

This is it, the last time New Jersey will see widespread 80s for quite a while. Big changes are ahead for the weekend, as we not only turn cooler but also considerably unsettled. Friday will be a nice weather day, especially as humidity levels slowly scale back from morning to afternoon. We will enjoy partly sunny skies and dry weather, with highs mainly in the lower 80s. By Saturday, cooler air will keep highs in the lower 70s — still a dry and pleasant day, just a different flavor of nice weather. On Sunday, a storm system comes into view that will deliver showers to North Jersey starting in the morning and then statewide through the afternoon and evening. Rain could become steady to heavy for a time late-day. That will kick off a stretch of cloudy days and continuous rain chances through much of next week, marking a relatively soggy transition from summer to autumn. The Autumnal Equinox arrives Tuesday at 8:05 p.m.

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Weather Hazards

Rainfall estimates for Sunday have risen to over an inch for parts of New Jersey, which is enough to ring alarm bells for ponding and flooding issues. The best chance for pockets of steady to heavy rain will be during the afternoon and evening hours.

In fact, the result of our impending extended stretch of wet weather could be multiple inches of rain by the end of next week. As the ground becomes increasingly saturated, any little downpour could spark a round of flooding or “big puddles.” Luckily, severe weather — wind, hail, and tornadoes — seems unlikely given our cooler temperatures and unfavorable atmospheric setup.

Climatological Context

September 18 is the 261st day of 2026.

Normal high temperatures range from 77 to 78 degrees, while normal low temperatures range from 57 to 60 degrees.

September is, on average, New Jersey’s fourth warmest and sixth driest month of the year.

Friday

Here we go. One more warm day. This will be the last time we see widespread 80s in New Jersey for a while. Maybe for the year?

Temperatures are hovering close to 70 degrees across New Jersey early Friday morning. It is a sticky, steamy start to the day. But give it a few hours. Even though temperatures stay on the warm side, humidity levels will slowly dial back through the day, making the air noticeably thinner and more comfortable by Friday afternoon.

Expect partly sunny skies, dry weather, and high temperatures mainly in the lower 80s. That is about 5 degrees above normal for mid-September. Soak in the warmth while it lasts.

Friday night turns seasonably cool under scattered clouds, with lows around 60.

Saturday

Saturday will be noticeably cool. But still nice — just a different flavor of pleasant weather.

Temperatures will swing from 5 degrees above normal Friday to around 5 degrees below normal Saturday. Highs will only reach the lower 70s.

Our weather should stay dry, and the cooler air should feel pretty refreshing. Clouds will increase as the day goes along, signaling that our next storm system will be getting closer.

Sunday

The rain machine gets turned back on Sunday. And unfortunately, it may stay on for a while.

Baseline forecast: Sunday will be mostly cloudy to overcast, and wet eventually. But most of the state should salvage a good chunk of the day.

Showers should arrive across North Jersey during the morning, generally north of Interstate 78. Central and southern New Jersey may very well stay dry for the first part of the day.

By Sunday afternoon and evening, statewide rain will become likely. And some of it could come down steadily or heavily for a time.

Rainfall totals over an inch are possible through Sunday night, raising the concern for some ponding and localized flooding. This does not look like a major severe thunderstorm setup, but a soaking rain can still make for lousy travel and outdoor conditions.

Temperatures will also vary quite a bit across the state, ranging from the mid 60s in soggy North Jersey to the mid 70s farther south (where the rain holds off until later).

Monday & Beyond

Monday stays unsettled, cloudy, breezy, and relatively cool.

Spotty showers will remain possible, with highs only in the upper 60s to around 70 degrees. That is a dramatic difference from our recent string of 80+ degree days, and a pretty convincing taste of October-ish air.

Daily rain chances look to continue through Tuesday, Wednesday, and Thursday. I do not think forecast models have really settled on which of those days will be the wettest yet — so it remains an uncertain call at this time. There will be periods of wet weather, and possibly sporadic breaks of sun.

By the end of next week, we could have several inches (3+ perhaps) of fresh rainfall in the gauge.

Temperatures will remain on the cool side for the duration too, with highs mainly in the 60s next week.

You have to admit, the timing for this change in the weather is fitting, even if it is not particularly pleasant. The Autumnal Equinox arrives Tuesday evening, officially ending summer and beginning fall.

New Jersey’s transition between the seasons is looking like quite the bumpy ride. A bumpy, soggy ride.

Dan Zarrow is Chief Meteorologist for Townsquare Media New Jersey. Follow him on Facebook for the latest forecast and realtime weather updates.