July in Waltham stays fresher than in 94% of U.S. towns
January nights here settle around 11°. Winter and summer sit 68° apart. Keep the boiler serviced for the months from October to April, which average under 50°.
A year in Waltham at a glance
Each month’s typical high and low, and what it brings.
What stands out about Waltham’s climate
Compared with towns across the U.S., with Waltham’s place in Maine beside it.
What a year in Waltham feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 152 frost-free days a year
In half of years the last 32° night comes by May 8 and the first by October 9. Frost and day counts come from NOAA’s station at E Surry, ME, 14 miles from the town’s center, at about the same height.
The 2023 USDA map puts Waltham’s center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −15°. 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 49 inches of rain a year
October is the wettest month and February the driest.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Waltham
97% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through May.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at E Surry, ME.
Living with Waltham’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
152 frost-free days in zone 5b. The last frost comes by May 8 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 9.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 6.3 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Waltham from natural hazards, river flooding is the largest share (50%); heat waves, cold waves, winter storms and ice storms together are 14%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Waltham and its neighbors
Osborn has the coldest January nights next door (10°, 1° colder). Differences under a degree are within what the 5 km grid can tell apart. Tap a town to see its climate.
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 Waltham averaged 1.6° warmer than the 1900s. The biggest change is in December (+3.4°).
A bigger shift than in 68% 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 Waltham compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Waltham’s place among Maine’s.
Waltham weather by month
Highs, lows and precipitation from NOAA’s grid at Waltham’s center. 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 30° | 11° | 4.0" | 11° – 28° |
| February | 32° | 13° | 3.1" | 9° – 29° |
| March | 40° | 22° | 3.9" | 25° – 38° |
| April | 53° | 32° | 4.2" | 39° – 48° |
| May | 65° | 42° | 3.8" | 49° – 58° |
| June | 73° | 51° | 4.1" | 59° – 67° |
| July | 79° | 58° | 3.3" | 64° – 71° |
| August | 78° | 57° | 3.2" | 64° – 71° |
| September | 69° | 49° | 3.9" | 55° – 64° |
| October | 57° | 39° | 5.4" | 44° – 55° |
| November | 46° | 29° | 4.8" | 33° – 42° |
| December | 35° | 19° | 4.9" | 21° – 35° |
| Year | 55° | 35° | 48.5" |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 9° to 29°. August is the most reliable, staying within 6°.
Where Waltham’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 Waltham’s center.
- Frost, freezing nights, 90° and 100° days, heating and cooling: E Surry, ME, 14 miles from the town’s center, at about the same height; 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 Waltham’s climate
What is the weather like in Waltham?
A typical July afternoon reaches 79°, a January night drops to 11°. Colder January nights than 92% of U.S. towns; cooler July afternoons than 94% of U.S. towns.
How cold does it get in Waltham in winter?
January nights average 11°. About 162 nights a year reach 32° or below and 12 reach 0° or below. In the coldest January of the last 30 years the month averaged 11°.
How hot does it get in Waltham?
July, with a typical high of 79° and a low of 58°. About 1 days a year reach 90° (E Surry, ME).
When is the first and last frost in Waltham?
In half of years the last spring frost (32°) comes by May 8 and the first fall frost by October 9, about 152 frost-free days, at E Surry, ME.
What growing zone is Waltham in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −15°.
What is the best time of year to visit Waltham?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Waltham getting warmer?
Yes: 1991–2020 averaged 1.6° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 68% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Waltham.
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.