Allentown, NJ Weather & Growing Conditions

Local forecast, frost dates, hardiness zone and planting guidance for Allentown, a borough in Mercer County, New Jersey.

Overnight

59°F

Mostly Cloudy

Mostly cloudy, with a low around 59. Southeast wind 0 to 5 mph.

7-day forecast for Allentown

When	Temp	Forecast	Wind	Precip
Overnight	59°F	Mostly Cloudy	0 to 5 mph SE	4%
Sunday	77°F	Rain Showers Likely	5 to 10 mph SE	57%
Sunday Night	58°F	Rain Showers Likely	5 to 10 mph W	70%
Monday	70°F	Partly Sunny then Chance Rain Showers	5 to 10 mph NE	30%
Monday Night	53°F	Chance Rain Showers	5 to 10 mph NE	30%
Tuesday	66°F	Chance Rain Showers	10 mph NE	35%
Tuesday Night	52°F	Chance Rain Showers then Mostly Cloudy	10 to 15 mph NE	35%
Wednesday	65°F	Slight Chance Rain Showers	15 mph NE	22%
Wednesday Night	52°F	Slight Chance Rain Showers	15 mph NE	22%
Thursday	64°F	Chance Rain Showers	10 to 15 mph NE	31%
Thursday Night	50°F	Chance Rain Showers	10 to 15 mph NE	38%
Friday	66°F	Chance Rain Showers	10 to 15 mph N	37%
Friday Night	50°F	Chance Rain Showers	10 mph N	37%
Saturday	70°F	Chance Rain Showers	10 mph N	30%

Forecast source: National Weather Service (api.weather.gov) for Allentown (40.179, -74.590). Updated through the day.

Growing snapshot for Allentown

Last spring frost

Apr 25

First fall frost

Oct 16

Growing season

173 days

Hardiness zone

More local growing data for Allentown: nearby ZIP 08691 weather · frost dates · planting calendar · New Jersey frost dates

Nearby towns & communities

Groveville Hamilton Square Hightstown Hopewell Lawrenceville Mercerville Pennington Princeton Robbinsville Center The College of New Jersey Titusville Trenton Twin Rivers White Horse Windsor Yardville

All New Jersey locations ›

Climate data from the nearest NOAA station, Hightstown 2 W, Nj (4.5 mi from Allentown). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 20, 2026.