Right now, if you step outside in Hamilton Square, you’re basically walking into a giant freezer that hasn't quite decided if it wants to be a swamp or a ski resort.
As of late Sunday evening, January 18, 2026, the temperature is hovering at a crisp 31°F. Honestly, though? It feels more like 25°F thanks to a persistent 7 mph wind coming out of the northwest. We’re currently in the middle of a messy mix of rain and snow. The humidity is sitting at a whopping 99%, so everything is just... damp.
Living in this corner of Mercer County means you’ve probably developed a sixth sense for "Jersey weather." It’s that unique brand of meteorological chaos where you can see all four seasons in a single Tuesday.
The Current State of Hamilton Square NJ Weather
We’re currently under a Winter Weather Advisory. It's been one of those days where the sky just looks like a wet wool blanket. Today's high barely hit 33°F, and the snow showers we saw earlier are expected to taper off as the night gets clearer.
If you’re planning your Monday commute, be ready for a sharp drop. We’re looking at a low of 19°F tonight.
What the next few days look like:
- Monday (MLK Day): It’ll be sunny, which is a nice change, but don't let the light fool you. The high is only 32°F, and with 12 mph winds, it's going to bite.
- Tuesday: This is the real kicker. The temperature is going to plummet to a high of 21°F. At night? We’re talking 11°F. Basically, stay inside.
- Wednesday: We start a slow climb back up to 35°F.
The weirdest part of the upcoming week is Thursday. We’re jumping all the way to 45°F. That’s a 24-degree swing from Tuesday’s high. Typical Hamilton Square, right?
Why Our Winters Feel So Much Colder
Technically, Hamilton Square falls into that "Humid Subtropical" zone (Köppen Cfa), but try telling that to someone scraping an inch of ice off their windshield at 6:00 AM.
According to data from the Rutgers University Meteorology Program, New Jersey has been warming up over the last few decades—about 4°F since 1900. But that warming doesn't mean "warmer" in the way we want. It actually makes the air hold more moisture. This is why our storms lately have felt more intense. Remember the remnants of Ida? Or the flash flooding this past July?
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In Hamilton Square, we average about 24 inches of snow a year. Most of that tends to dump in February, which is historically our snowiest month. But January 2026 is already showing its teeth.
The Growing Season Shift
If you’re one of the many people here who spends too much money at the local garden centers, you’ve probably noticed the "frost creep."
Historically, our first frost hits somewhere between October 21 and October 31. The last frost usually bows out by late April. However, the USDA Plant Hardiness Zone map for our area recently shifted. Many parts of Hamilton Township moved from Zone 6b to Zone 7a.
What does that actually mean for your backyard?
Well, it means we can grow things now that wouldn't have survived twenty years ago. But it also means pests like ticks and mosquitoes aren't dying off in the winter like they used to. It’s a trade-off. You get nicer hydrangeas, but you have to check your ankles for deer ticks in December.
Surviving the Summer Humidity
Let’s talk about the other side of the coin. July in Hamilton Square is... a lot.
The average high is around 85°F, but with the humidity off the Delaware River, the heat index frequently cracks 100°F. July is also our wettest month, averaging nearly 5 inches of rain. It’s not a gentle spring rain, either. It’s usually a massive, 20-minute thunderstorm that turns the roads into rivers and then vanishes, leaving the air feeling like a sauna.
According to reports from NJWeather.org, we’re seeing more "dull, cloudy days" even when it isn't raining. It’s just that thick, hazy atmosphere that makes you want to live inside your air conditioner.
Practical Steps for Hamilton Square Residents
Weather here isn't just something to chat about at the grocery store; it’s something you have to prep for.
- Watch the Tuesday Cold Snap: With temperatures dropping to 11°F Tuesday night, make sure your outdoor pipes are insulated. If you have a drafty basement, now is the time to crack the faucets to a drip.
- Salt the Sidewalks Now: Since we have a 56% chance of snow continuing into the night and temperatures dropping well below freezing, that slush on the ground is going to turn into a sheet of glass by morning.
- Check Your Sump Pump: We’re seeing a trend of "dry winters" followed by "flash flood springs." Given the 99% humidity and the rain/snow mix today, the ground is getting saturated. Ensure your pump is cleared of debris before the "big thaw" on Thursday when we hit 45°F.
- Gardening Prep: If you’re a local gardener, keep an eye on those mid-week temperature swings. These sudden jumps to the 40s can trick some of your early perennials into thinking it’s spring, only to have them killed off by the next 10°F night. Keep them mulched deep.
Hamilton Square NJ weather is a lot of things, but "boring" isn't one of them. Keep your ice scraper handy, keep your umbrella in the trunk, and maybe keep a heavy coat next to a light jacket. You're probably going to need both by Friday.