Flood Watch: NJ rain estimates and severe storm threat has gone up for Thursday

The Bottom Line

The forecast for Thursday’s storm system is locked in, and it is trending wetter and stormier. Your outdoor plans for the afternoon and especially evening time frame are in big trouble, as a push of steady to heavy rain may produce flooding and severe weather concerns. Friday will be a better, brighter weather day with only a stray shower chance along New Jersey’s southern coast. But this weekend marks the return of unsettled weather, especially on Saturday, which looks quite wet through at least the morning. It will probably be showery, cloudy, and relatively cool through the afternoon too. Sunday’s forecast is better, as showers wrap up, skies will start to clear, and temperatures will warm up again. So at least the second half of the weekend will likely be salvaged. Next week trends mainly dry and comfortable.

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Weather Hazards

A Flood Watch has been issued for 18 of New Jersey’s 21 counties — all but Sussex, Warren, and Cape May — from Thursday afternoon through late Thursday night. Over an inch of rain could fall in a relatively short period of time, producing ponding on roadways and overwhelming drainage systems. That could make travel conditions difficult during and after downpours, especially heading into and through Thursday evening’s commute.

Flash flooding is not always a "biblical" wave of water swallowing entire towns. It can be a big puddle, an inundated roadway, travel problems, or a swamped car. Flooding is dangerous stuff, so it is important to take it seriously.

There is also an elevated risk of severe weather Thursday. All three standard severe thunderstorm threats — wind, hail, and tornadoes — are on the table. (However, the flooding threat is the bigger concern, in my opinion.)

By definition, any thunderstorm contains lightning. Therefore, every thunderstorm is potentially dangerous. When the sky darkens up or thunder starts to roar, it is time to seek shelter inside a sturdy building until the storm passes.

Saturday’s storm system may also pose a marginal flooding and severe weather threat for New Jersey. With over an inch of total rainfall possible, if not likely, it is worth putting a preemptive yellow alert icon on the five-day forecast.

Climatological Context

August 20 is the 232nd day of 2026.

Normal high temperatures range from 84 to 85 degrees, while normal low temperatures range from 64 to 68 degrees.

August is, on average, New Jersey’s second hottest and second wettest month of the year.

Thursday

Thursday morning: All good and pretty pleasant across New Jersey. Most temperatures are in the 60s to start the day, with 70s limited to urban and coastal areas only.

But the bottom line for Thursday is simple. Dry to wet. Very wet.

Clouds will fill in through Thursday morning. The weather will stay dry through at least early afternoon, so the first part of the day looks fine for errands, travel, and outdoor plans. High temperatures will reach 80 to 85 degrees.

Then rain will start pushing in around mid afternoon, eventually reaching every corner of the state around late afternoon

The big question in my mind is just how humid it gets. The bigger our influx of warm, moist air, the stronger the thunderstorms and the heavier the rain will be.

Strong thunderstorms and heavy downpours are possible Thursday afternoon and especially Thursday evening. Rainfall estimates have gone up, with over an inch of total rain possible for most of the state. A period of steady to heavy rain is likely Thursday evening, tapering by midnight or so.

Skies will clear overnight, with fairly comfortable low temperatures in the mid 60s.

Friday

Friday will be a better, brighter weather day for New Jersey.

Expect partly sunny skies, highs around 80 degrees, and a generally quieter setup.

There is only a slight chance of a stray shower in the afternoon, clipping southern and coastal New Jersey.

Saturday

I am very careful about forecasting rain over summer weekends. But I have to admit this weekend will have some weather challenges. Especially on Saturday.

A stalled or slow-moving cold front will keep wet weather chances over New Jersey Saturday. Current model guidance suggests the steadiest rain will be in the morning, becoming spottier in the afternoon.

It will be cloudy and cooler too, with highs only in the 70s. (Some models paint highs only in the 60s — gross!)

Saturday’s storm system could produce over an inch of total rainfall in spots. That may be enough to cause some ponding, poor drainage flooding, and tricky travel. A stronger thunderstorm cannot be ruled out too.

Sunday & Beyond

I am fully confident that Sunday will be the better day of the weekend. It is just a matter of how quickly skies will clear

Morning showers will still be possible. After that, breaks of sun should slowly develop, allowing temperatures to warm back into the lower 80s. So while Sunday may not start perfectly, the second half of the weekend should generally be salvageable.

Looking beyond Sunday, next week trends mainly dry and comfortable. High temperatures will hover around 80 degrees most days, with humidity on the low side. Rain chances will remain low too. Welcome news after a humid and stormy few weeks.

Until then, umbrellas up, windshield wipers on, and stay safe out there.

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