Climate and monthly weather forecast
Merrimack, NH


The climate of Merrimack

Merrimack, New Hampshire holds a position within the climatic zone known by the Köppen climate classification as Dfb. This signifies a humid continental climate, with no dry season and summertime warmth. Weather perceptions in Merrimack follow a relatively distinct pattern, due, in part, to its geographical location in the northeastern United States.

Throughout the calendar year, Merrimack experiences significant temperature shifts. From January through December, the highest recorded temperatures fluctuate between 30.6°F (-0.8°C) and 81.7°F (27.6°C). Meanwhile, the spectrum for the lowest temperature readings extends from 18°F (-7.8°C) to 61°F (16.1°C). A noticeable peak happens in July and a trough in winter months - January and February. With regard to humidity, the relative levels of moisture in the atmosphere generally maintain a degree of consistency, within the range of 72% to 81%.

Rainfall also portrays a particular pattern in Merrimack's climate. Throughout the year, precipitation levels register between 0.75" (19mm) to 1.38" (35mm). Although devoid of any pronounced dry or wet seasons, the city receives marginally higher rainfall in October. On the other hand, snowfall is decidedly a winter phenomenon. It tends to peak in January and December with 2.4" (61mm) and 2.99" (76mm) respectively and falls to virtually nonexistent by mid-spring.

The best time to visit Merrimack

Considering sunshine hours, temperature, and precipitation, the ideal period to visit Merrimack is arguably between June and September. During these months, temperatures register between a comfortable 66.9°F (19.4°C) and 81.7°F (27.6°C) — optimal for outdoor activities. Furthermore, the daylight hours extend from 14.7 hours to 15.3 hours, providing plenty of sunlight for sightseeing. Plus, relative humidity hovers around 75%, creating a pleasant balance by not being too dry or damp.

The worst time to visit Merrimack

One might want to avoid visiting Merrimack during the cold winter months particularly from December to February. Temperatures during this time tend to dip down and range from a chilly 18°F (-7.8°C) to roughly 33.3°F (0.7°C). Moreover, snowfall is prevalent during these winter months, which could restrict outdoor activities. Reduced daylight hours, which range from 9.1 hours to 10.6 hours, further limit sightseeing opportunities.

Spring weather in Merrimack

Springtime in Merrimack brings about a noticeable warming trend and the gradual retreat of winter. From March to May, temperatures climb steadily from 41.2°F (5.1°C) to 66.9°F (19.4°C). Meanwhile, the daylight hours also expand from 12 hours to approximately 14.7 hours a day, extending the outdoor hours. During this season, the city experiences average rainfall ranging from 1.06" (27mm) to 0.98" (25mm) and reduces snowfall from 1.85" (47mm) in March to virtually none in May.

Summer weather in Merrimack

Summer in Merrimack typically earmarks the warmest temperatures and longest daylight hours of the entire year. High temperatures stretch between 74.5°F (23.6°C) in June and peak at 81.7°F (27.6°C) in July. Daylight hours eclipse at 15.3 hours in June, providing ample light for outdoor pursuits. Rainfall peaks at 1.3" (33mm) in July but steadies to about 1.1" (28mm) in August.

Autumn weather in Merrimack

Autumn signals a retreat from the summer's warmth as temperatures cool from 72.1°F (22.3°C) in September to a brisk 46.6°F (8.1°C) by November. Daylight hours shorten as well, from 12.5 hours at the start of the season to approximately 9.8 hours by November. Precipitation in autumn is characterized by an increase, with October receiving the highest rainfall of the year at 1.38" (35mm).

Winter weather in Merrimack

Winter in Merrimack is marked by cold temperatures and notable snowfall. The period from December to February sees high temperatures recede from 36.3°F (2.4°C) to 30.6°F (-0.8°C) and lower temperatures fall to 18°F (-7.8°C) in the coldest month, January. Snowfall during this period ranges from 2.99" (76mm) in December to 2.4" (61mm) in January. Daylight hours shrink to a yearly low of 9.1 hours by December, with a slight increase to 10.6 hours by February.

Weather in January

January for Merrimack, New Hampshire tends to reveal a winter's firm grip with a moderate level of precipitation. Amid this month, the city also experiences shorter daylight hours, typically amounting to approximately 9.4 hours. Weather in January »

Weather in February

February may feel slightly warmer than January, but the winter conditions persist in Merrimack. While evaluating the visibility, it's worth noting that the rate is relatively decent for the road users to navigate. The city gets the most snowfall in February 2.32" (59mm), making it ideal for winter activities, particularly skiing. Weather in February »

Weather in March

Eagerly awaiting the change of seasons, residents of Merrimack prepare for the shifts in weather as March approaches. With the arrival of spring, an increase in daylight hours can be observed. During this transition month, snowfall dips to 1.85" (47mm), indicating the receding winter. Weather in March »

Weather in April

Throughout April in Merrimack, the weather experiences a transformation towards more warmer and pleasant conditions. The citizens start replacing their warm layers with light clothes, as they witness the introduction of a refreshing change in the atmosphere. Weather in April »

Weather in May

With rising temperatures, blossoming flowers, and the advent of a humid climate, May in Merrimack offers a refreshing setting. It's a season wherein the weather gently nudges inhabitants towards outdoor recreational activities. The fluctuations in pressure patterns also start becoming significant around this time. Weather in May »

Weather in June

June brings the onset of summer to Merrimack, with fluctuations in temperature and humidity levels that are higher than the yearly average. Longer hours of daylight and increased sunshine enable outdoor enthusiasts to plan events and activities. Weather in June »

Weather in July

July in Merrimack aces as the warmest month of the year, with average temperatures hitting the peaks. Choosing the right attire that complements the hot and humid weather becomes more critical at this time. Outdoor events and gatherings increasingly embrace late evenings to beat the heat. Weather in July »

Weather in August

As summer begins to bid goodbye in August, Merrimack observes a marginal drop in daily high temperatures. Nonetheless, the hot and humid conditions act as a reminder of the summer peak in July. A meandering walk along the city lanes in late afternoon promises a calm and enjoyable experience. Weather in August »

Weather in September

September carries a hint of autumn in the air as Residents of Merrimack slightly feel the diminishing warmth. Despite a increasing humidity, the breeze carries a pleasant nip that adds to the city's climate charm. Subtle changes in the landscape become evident as leaves start turning different hues. Weather in September »

Weather in October

The October weather in Merrimack starts leaning towards the cooler spectrum, indicating the onset of fall. With dropping temperatures, the necessity of wearing warm clothing emerges once again among the locals. The city paints a beautiful picture of different shades of fall, encouraging local tourism. Weather in October »

Weather in November

As November arrives in Merrimack, winter hints at its advent with a steady drop in temperatures. The days become shorter as darkness creeps in relatively earlier; a clear sign that winter is knocking at the door. The city's topography, combined with dropping temperatures, gives rise to the need for warmer clothing. Weather in November »

Weather in December

December marks the full arrival of winter in Merrimack with accompanying cold winds. The city is adorned with festive decorations, complementing the beauty of the snow-covered landscapes. A considered viewing reveals the city preparing to welcome the New Year, braving the icy grip of winter. Weather in December »

Frequently asked questions

What is the coldest month in Merrimack?

Merrimack records the coldest temperatures in January, averaging a high of 30.6°F (-0.8°C) and a low of 18°F (-7.8°C).

What is the driest month in Merrimack?

January is the month with the least rainfall. Rain falls for 4.1 days and accumulates 0.75" (19mm) of precipitation.

How many days does it rain in Merrimack?

Throughout the year, there are 104.4 rainfall days, and 12.95" (329mm) of precipitation is accumulated.

When does it snow in Merrimack?

Months with snowfall are January through May, October through December.

How much does it snow in Merrimack?

Throughout the year, in Merrimack, New Hampshire, there are 26.1 snowfall days, and 11.54" (293mm) of snow is accumulated.

When is the lowest UV index in Merrimack?

January through March, November and December, with an average maximum UV index of 2, are months with the lowest UV index in Merrimack.

What is the most humid month in Merrimack?

February is the most humid month, with an average relative humidity of 81%.

What is the month with the least sunshine in Merrimack?

The month with the least sunshine in Merrimack, New Hampshire, is February, with an average of 4.6h of sunshine.

When is Daylight Saving Time (DST) in Merrimack?

On Sunday, March 10. 2024, at 2:00 am, Daylight Saving Time starts in Merrimack, and the time zone changes from EST to EDT. Daylight Saving Time ends Sunday, November 3. 2024, at 2:00 am, and the time zone reverts from EDT to EST.

What is the least humid month in Merrimack?

April is the least humid month, with an average relative humidity of 72%.

When it does not snow in Merrimack?

In Merrimack, New Hampshire, snow does not fall in June through September.

When are the longest days in Merrimack?

June has the longest days of the year in Merrimack, New Hampshire, with an average of 15h and 18min of daylight.

When is the highest UV index in Merrimack?

The months with the highest UV index are June through August, with an average maximum UV index of 6.

What is the warmest month in Merrimack?

July is the month when Merrimack sees the average highest temperatures, with a high of 81.7°F (27.6°C) and a low of 61°F (16.1°C).

What month has the most sunshine in Merrimack?

The month with the most sunshine in Merrimack, New Hampshire, is August, with an average of 10.4h of sunshine.

What is the rainiest month in Merrimack?

The month with the most rainfall in Merrimack is October, when the rain falls for 9.4 days and typically aggregates up to 1.38" (35mm) of precipitation.

What is the snowiest month in Merrimack?

December is the month with the most snowfall in Merrimack. Snow falls for 4 days and accumulates 2.99" (76mm) of snow.

What is the month with the shortest days in Merrimack?

December has the shortest days of the year, with an average of 9h and 6min of daylight.

Average pressure
Merrimack, NH

Average pressure - Merrimack, NH

The month with the highest atmospheric pressure is November (30.07"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).


Average wind speed
Merrimack, NH

Average wind speed - Merrimack, NH

The windiest month (with the highest average wind speed) is January (8.3mph).
The calmest month (with the lowest average wind speed) is August (5.1mph).


Average rainfall
Merrimack, NH

Average rainfall - Merrimack, NH

The wettest month (with the highest rainfall) is October (1.38").
The driest month (with the least rainfall) is January (0.75").


Average rainfall days
Merrimack, NH

Average rainfall days - Merrimack, NH

The month with the highest number of rainy days is June (12.1 days).
The month with the least rainy days is January (4.1 days).


Average snowfall
Merrimack, NH

Average snowfall - Merrimack, NH

The month with the highest snowfall is December (2.99").
The months with the least snowfall are June, July, August and September (0").


Average snowfall days
Merrimack, NH

Average snowfall days - Merrimack, NH

The month with the highest number of snowfall days is January (7.1 days).
The months with the least snowfall days are June, July, August and September (0 days).


Average daylight / Average sunshine
Merrimack, NH

Average daylight / Average sunshine - Merrimack, NH

The month with the longest days is June (Average daylight: 15h and 18min).
The month with the shortest days is December (Average daylight: 9h and 6min).

The month with the most sunshine is August (Average sunshine: 10h and 24min).
The month with the least sunshine is February (Average sunshine: 4h and 36min).


Average sunshine days
Merrimack, NH

Average sunshine days - Merrimack, NH

The months with the most sunshine days are January and December (21.3 days).
The month with the least sunshine days is June (16.7 days).


Average UV index
Merrimack, NH

Average UV index - Merrimack, NH

The months with the highest UV index are June, July and August (UV index 6).
The months with the lowest UV index are January, February, March, November and December (UV index 2).


Average visibility
Merrimack, NH

Average visibility - Merrimack, NH

The months with the highest visibility are January, April, November and December (6mi).
The months with the lowest visibility are February, March, May, June, July, August, September and October (5mi).


Merrimack, New Hampshire, USA

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