Merrimack, Nashua Weather
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Climate of Merrimack: monthly averages
Based on 25 years of satellite and reanalysis data (2001-2025), July is usually the hottest month in Merrimack, with average daytime highs around 27°C. January is the coolest, when nights typically fall to about -10°C and frost is possible on the coldest nights. That is a wide yearly range of roughly 37°C, so the seasons feel very different from each other.
The area receives about 1180 mm of rain in a typical year. Most of it falls from April, June, October and December, and October is the wettest month at roughly 123 mm.
For outdoor plans and travel, May and July to September usually offer the most comfortable weather in Merrimack, with mild days and relatively little rain.
| Month | Avg high | Avg low | Rainfall | Humidity |
|---|---|---|---|---|
| Jan | -1° | -10° | 73 mm | 89% |
| Feb | 1° | -9° | 83 mm | 88% |
| Mar | 5° | -4° | 99 mm | 83% |
| Apr | 13° | 1° | 102 mm | 79% |
| May | 19° | 8° | 98 mm | 79% |
| Jun | 24° | 13° | 115 mm | 80% |
| Jul | 27° | 17° | 97 mm | 78% |
| Aug | 27° | 16° | 95 mm | 76% |
| Sep | 23° | 12° | 90 mm | 76% |
| Oct | 16° | 6° | 123 mm | 79% |
| Nov | 9° | 0° | 94 mm | 82% |
| Dec | 2° | -5° | 111 mm | 87% |
Source: NASA POWER (MERRA-2 reanalysis), averaged over the roughly 50 km grid area around Merrimack. Values describe typical conditions, not a forecast.
About Merrimack weather
Merrimack, in New Hampshire's humid continental climate, from coast to White Mountains, is positioned about 26 km south of Manchester. The warmer months mean mild summers (June–August). Finally, there's cold, snowy winters (December–February), colder in the mountains. This page shows live, auto-refreshing weather for Merrimack: current conditions, an hourly breakdown, a 16-day outlook, a date-lookup tool for any past or future date, and real-time air quality, sourced from Open-Meteo. Local timezone: America/New_York.
Frequently asked questions
Merrimack is about 26 km south of Manchester, in New Hampshire.
Merrimack sees cold, snowy winters (December–February), colder in the mountains.
The live current conditions, hourly forecast and 16-day outlook above are pulled in real time for Merrimack's exact coordinates. No fixed schedule, the page updates whenever you load it.
July is usually the hottest month in Merrimack, with average daytime highs of about 27°C and nights around 17°C.
The coldest nights come in January, when the average low is about -10°C and daytime highs reach around -1°C. Frost is possible on clear, calm nights.
Merrimack receives about 1180 mm of rain in a typical year. October is the wettest month at roughly 123 mm, and the main rainy period is April, June, October and December.
May and July to September usually offer the most comfortable weather in Merrimack, with mild daytime temperatures and little rain.
In November Merrimack typically sees daytime highs near 9°C and lows near 0°C, with about 94 mm of rain over the month and average humidity around 82%. Check the live forecast above for this week's actual conditions.
Up to 16 days ahead using the extended forecast and date picker above; further-out or historical dates use the same date lookup tool.
The current temperature for Merrimack updates automatically at the top of this page — scroll to the hourly strip below to see how it's expected to change over the day.
Merrimack's day-to-day weather follows the broader pattern of New Hampshire described above. See the hourly weather forecast or the air quality index for more detail.