Photo: JERRYE & ROY KLOTZ MD · CC BY-SA 3.0Precipitation in Mendham tops that of 87% of U.S. towns: 51 inches a year
On a normal January night the air cools to about 20°. Winter and summer sit 64° apart. Tender plants can go out after about April 18; in half of years the first frost comes by October 27.
A year in Mendham at a glance
Each month’s typical high and low, and what it brings.
What stands out about Mendham’s climate
Compared with towns across the U.S., with Mendham’s place in New Jersey beside it.
What a year in Mendham feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 189 frost-free days a year
In half of years the last 32° night comes by April 18 and the first by October 27. Frost and day counts come from NOAA’s station at Canoe Brook, NJ, 13 miles from the town’s center, 380 ft lower.
The 2023 USDA map puts Mendham’s center in zone 6b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 0°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 30 inches of snow a winter
Snow, measured at Pottersville 2 Nnw, NJ, falls mostly in February. Precipitation (rain plus melted snow) adds up to 51 inches a year; July is the wettest month and February the driest. Rain or snow falls on about 120 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Mendham
84% of the work is heating. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Canoe Brook, NJ.
Living with Mendham’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
189 frost-free days in zone 6b. The last frost comes by Apr 18 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 27.
Months with highs of 62–84° and lows of 40° or more: May, June, August, September and October. 5.9 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Mendham from natural hazards, river flooding is the largest share (74%); heat waves, cold waves, winter storms and ice storms together are 11%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Mendham and its neighbors
Every town next door is within a degree of Mendham in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Mendham’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Mendham, NJ | 20° | 84° | 51" | 30" |
| Middleborough Center, MA | 20° | 84° | 51" | 31" |
| Cranston, RI | 20° | 83° | 49" | 37" |
| Buckhannon, WV | 23° | 83° | 50" | 39" |
| Connellsville, PA | 21° | 84° | 46" | 24" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Mendham averaged 2.2° warmer than the 1900s. The biggest change is in December (+3.7°).
A bigger shift than in 94% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Mendham compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Mendham’s place among New Jersey’s.
Mendham weather by month
Highs, lows and precipitation from NOAA’s grid at Mendham’s center; snow, wet days and snow on the ground from Pottersville 2 Nnw, NJ. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 38° | 20° | 3.8" | 7.4" | 11 | 11 | 20° – 36° |
| February | 41° | 22° | 3.0" | 10.3" | 8 | 14 | 19° – 38° |
| March | 49° | 29° | 4.2" | 5.8" | 10 | 6 | 33° – 48° |
| April | 61° | 38° | 4.1" | 0.7" | 10 | 0 | 46° – 55° |
| May | 71° | 48° | 4.2" | 0.0" | 12 | 0 | 55° – 65° |
| June | 80° | 57° | 4.9" | 0.0" | 12 | 0 | 65° – 71° |
| July | 84° | 62° | 4.9" | 0.0" | 11 | 0 | 69° – 77° |
| August | 83° | 60° | 4.6" | 0.0" | 10 | 0 | 67° – 75° |
| September | 76° | 54° | 4.7" | 0.0" | 9 | 0 | 62° – 69° |
| October | 64° | 42° | 4.7" | 0.3" | 9 | 0 | 48° – 60° |
| November | 53° | 33° | 3.6" | 0.3" | 9 | 0 | 38° – 48° |
| December | 42° | 25° | 4.6" | 4.8" | 10 | 5 | 27° – 45° |
| Year | 62° | 41° | 51.1" | 29.6" | 120 | 37 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 19° to 38°. June is the most reliable, staying within 7°.
Where Mendham’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Mendham’s center.
- Snow: Pottersville 2 Nnw, NJ.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Canoe Brook, NJ, 13 miles from the town’s center, 380 ft lower; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Mendham’s climate
What is the weather like in Mendham?
A typical July afternoon reaches 84°, a January night drops to 20°, and about 30 inches of snow falls in a normal winter. Colder January nights than 57% of U.S. towns; cooler July afternoons than 56% of U.S. towns.
How cold does it get in Mendham in winter?
January nights average 20°. About 118 nights a year reach 32° or below and 1 reach 0° or below. In the coldest January of the last 30 years the month averaged 20°.
How much snow does Mendham get?
About 30 inches in a normal winter at Pottersville 2 Nnw, NJ, most of it in February, with snow on the ground about 37 days a year.
How hot does it get in Mendham?
July, with a typical high of 84° and a low of 62°. About 29 days a year reach 90° and 1 reach 100° (Canoe Brook, NJ).
When is the first and last frost in Mendham?
In half of years the last spring frost (32°) comes by April 18 and the first fall frost by October 27, about 189 frost-free days, at Canoe Brook, NJ.
What growing zone is Mendham in?
Zone 6b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 0°.
What is the best time of year to visit Mendham?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Mendham getting warmer?
Yes: 1991–2020 averaged 2.2° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 94% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Mendham.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.