Rocky Hill, NJ climate
Rocky Hill has chilly winters and warm summers, with plenty of rain. A typical July afternoon reaches 87°, a January night drops to 23°, and about 21 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Rocky Hill feels like
Winter
Spring
Summer
Fall
Rocky Hill weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 41° | 23° | 3.5" | 6.8" | 10 | 24° – 39° |
| February | 43° | 24° | 2.8" | 6.7" | 8 | 22° – 40° |
| March | 51° | 31° | 4.1" | 3.6" | 10 | 35° – 50° |
| April | 64° | 40° | 3.7" | 0.2" | 11 | 48° – 56° |
| May | 73° | 50° | 4.1" | 0 | 12 | 57° – 67° |
| June | 82° | 59° | 4.5" | 0 | 11 | 67° – 74° |
| July | 87° | 65° | 5.1" | 0 | 10 | 71° – 79° |
| August | 85° | 63° | 4.3" | 0 | 10 | 69° – 77° |
| September | 78° | 56° | 4.1" | 0 | 9 | 64° – 71° |
| October | 66° | 44° | 4.2" | 0.1" | 10 | 50° – 62° |
| November | 55° | 35° | 3.3" | 0.1" | 9 | 40° – 50° |
| December | 45° | 28° | 4.3" | 3.5" | 10 | 29° – 48° |
| Year | 64° | 43° | 47.9" | 21.0" | 121 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Rocky Hill
Rocky Hill gets 48 inches of rain and melted snow a year. July is the wettest month and February the driest. Rain or snow falls on about 121 days a year.
About 173 frost-free days a year
In half of years the last 32° night comes by April 25 and the first one by October 16. That leaves about 173 frost-free days for gardens, shorter than 57% of U.S. towns.
Heating and cooling a home in Rocky Hill
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Rocky Hill, 85% of that work is heating and 15% is cooling, so the furnace matters far more than the air conditioner.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
Rocky Hill and its neighbors
Rocky Hill borders 2 towns with climate data. January nights across them vary by 0.3°. Montgomery has the coldest January nights (23°) and Franklin the hottest July afternoons (87°). Rocky Hill’s January low is 23° and its July high 87°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Rocky Hill compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Rocky Hill averaged 2.3° warmer than the 1900s. The biggest change is in December (+3.8°). The shift is larger than in 99% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Rocky Hill’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. December swings the most: between 1991 and 2020 its average temperature ranged from 29° to 48°. September is the most reliable, staying within 7°.
Common questions about Rocky Hill’s climate
What is the coldest month in Rocky Hill?
January, with a typical high of 41° and a low of 23°.
What is the hottest month in Rocky Hill?
July, with a typical high of 87° and a low of 65°. About 26 days a year reach 90°.
How much snow does Rocky Hill get?
About 21 inches in a normal winter, most of it in January.
When is the first frost in Rocky Hill?
In half of years the first 32° night comes by October 16, and the last spring frost by April 25.
What is the rainiest month in Rocky Hill?
July, with 5.1 inches of rain and melted snow. The year totals 48 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Rocky Hill itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Bound Brook 2w, NJ (11 mi, snow) and Hightstown 2 W, NJ (10 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.