Yes. Mice are nocturnal to crepuscular, meaning they're most active shortly after dark and again in the hours before dawn, resting for much of the day in short bouts. Poor eyesight makes them rely on smell, whiskers, and memorized wall routes to move safely at night. That's why homeowners typically hear scratching, scurrying, or squeaking in walls and ceilings after dark rather than spotting mice directly. A mouse seen repeatedly during the day can signal a larger population or a scarce food supply.

When do mice come into the house?

The heaviest entry into New Hampshire homes happens in fall, as outdoor food disappears and nights turn cold ahead of Manchester's roughly October 19 first frost. Mice can squeeze through any gap a quarter inch or larger — about the width of a pencil — so exclusion work is most effective when finished before mid-October. Waiting until after the frost usually means sealing mice inside rather than keeping them out, since populations are already establishing themselves in walls and basements.

Do mice squeak at night?

Yes. Squeaking, along with scratching and scurrying, is a classic sign of active mice traveling their wall runways after dark. Because mice are nocturnal, these sounds typically start shortly after the house goes quiet and can continue in bursts through the night, picking up again before dawn. If you're hearing squeaks repeatedly from the same wall or ceiling area, it usually means mice have an established nest nearby rather than a single mouse passing through.

Do house mice breed in winter?

Yes. Unlike many pests that go dormant, house mice breed year-round in heated New Hampshire homes, with females capable of producing multiple litters in quick succession. That means a small fall intrusion of just one or two mice can grow into a visible infestation by midwinter if left unaddressed. Deer mice, by contrast, are more seasonal, moving indoors mainly in fall and winter. This continuous indoor breeding is the main reason acting at the first sign of mice matters.

What does scratching in the walls at night mean?

Nighttime scratching in walls or ceilings is one of the earliest and most reliable signs of active rodents traveling their runways after dark. It's typically mice or rats moving between a nest and a food source, and the sounds often line up with dusk and pre-dawn activity peaks. If you hear this, inspect nearby areas for droppings, gnaw marks, or shredded nesting material, and consider sealing entry points before the activity grows into a larger infestation.

How do I tell a deer mouse from a house mouse?

Deer mice have a sharply two-toned coat — brown or gray on top with a white belly — plus a bicolored tail and noticeably large eyes and ears. House mice are uniformly gray-brown with a single-color, nearly hairless tail. The distinction matters in New Hampshire because deer mice are the primary carriers of hantavirus and tend to move indoors seasonally in fall, while house mice live indoors year-round and breed continuously in heated homes.

What's the hantavirus risk with deer mice?

Deer mice are the primary carrier of hantavirus pulmonary syndrome, a serious respiratory illness transmitted mainly by inhaling dust from dried droppings, urine, or saliva. The virus becomes airborne once waste dries out, so never dry-sweep or vacuum deer-mouse droppings. Instead, wet the area with disinfectant, wear gloves and a mask, and ventilate before cleaning; for attic infestations, professional cleanup is safer. Contact a doctor promptly if flu-like symptoms develop after exposure to rodent droppings.

How far do mice travel indoors?

Mice rarely travel more than about 30 feet from their nest to a food source, which is why activity tends to stay concentrated in one area of a home — often a kitchen, pantry, or wall near a food supply. This limited range is also why snap traps work best when placed roughly 10 feet apart along walls and near droppings, rather than scattered randomly throughout a house. Persistent activity in one zone usually points to a nearby, established nest.

Daniel Brady · NH-Licensed Pesticide Applicator · License #782664

|Reviewed by Daniel Brady

Where Do Mice Go in the Winter? NH Mouse Timing Guide

Nocturnal Rodents

Mice do not migrate or hibernate. House mice remain indoors year-round and breed continuously in warm homes, while deer mice move inside in fall and winter as outdoor food disappears and temperatures fall below Manchester's ~October 19 first frost. Indoors they nest in wall voids, attics, basements, and stored boxes, staying within about 30 feet of a food source. Mice are nocturnal, peaking shortly after dark and again before dawn, so homeowners usually hear them at night rather than see them.

At a glance

Activity pattern: Nocturnal/crepuscularPeaks shortly after dark and again before dawn; rests ~12 hrs/day — UNH Extension
Winter behavior: No hibernationHouse mice breed indoors all winter; deer mice move in seasonally — UNH Extension
Peak home-entry: Sept–NovFall entry as outdoor food vanishes ahead of first frost (~Oct 19, Manchester — NOAA)
Entry gap size: ≥¼ inch ("if a pencil fits")Seal to ¼-inch to exclude mice — UNH Extension

Activity pattern
Nocturnal/crepuscular
Peaks shortly after dark and again before dawn; rests ~12 hrs/day — UNH Extension
Winter behavior
No hibernation
House mice breed indoors all winter; deer mice move in seasonally — UNH Extension
Peak home-entry
Sept–Nov
Fall entry as outdoor food vanishes ahead of first frost (~Oct 19, Manchester — NOAA)
Entry gap size
≥¼ inch ("if a pencil fits")
Seal to ¼-inch to exclude mice — UNH Extension

The timing answer

The short of it

The verdict · nocturnal rodents

Active at night, year-round

Mice don't go anywhere for winter — they move into heated New Hampshire homes in fall and stay active and breeding indoors all season, foraging at night.

NH activity calendar

When are they active — the whole year at a glance

Mice are active in New Hampshire year-round, but the pattern splits in two: an outdoor population boom in summer and a separate, higher-risk surge of mice moving into homes each fall as temperatures drop toward the first frost.

12-month activity · New Hampshire

Peak · Oct, NovYou are here · Aug

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

PeakActiveBuildingDecliningDormantCurrent season · Summer

Best window to act · Seal entry points (any gap ≥¼ inch) before mid-October, ahead of the frost-driven indoor migration.

What else peaks thenOct Nov

Peak months = highest risk of mice entering NH homes, anchored to Manchester's first-frost date (Oct 19, 50% probability — NOAA 1991–2020).

Daily activity

What time of day are they active?

Nocturnal

Mice have poor eyesight but keen smell and hearing; they travel along walls and edges in dim light, which is why you hear them before you see them.

Mice are nocturnal, so a mouse seen repeatedly in daylight can signal a large population or scarce outdoor food — though house mice are somewhat more flexible than rats. Nighttime scratching, scurrying, and squeaking in walls or ceilings after dark is the classic early sign of activity.

A day in their clock

Dawn

Day

Dusk

Night

Dusk / after dark (first hours after lights-out)peak
Late nightactive
Pre-dawn (hours before sunrise)peak
Daytimelow

Where they go in winter

Winter behavior

"Where do mice go in the winter?" is the #1 question for this page — the honest answer is that they come to you.

Overwintering strategy

Active all winter

Neither house mice nor deer mice hibernate. House mice stay indoors year-round and breed continuously in heated space, while deer mice migrate in from fields, woodpiles, and sheds into garages, crawlspaces, attics, and wall voids, caching seeds to survive. Nests cluster in wall voids, attics, basements, and stored boxes, usually within about 30 feet of a food source.

Move in
Late September through November, as outdoor food disappears and temperatures fall toward and past the ~Oct 19 Manchester frost.
Active all winter
Neither house mice nor deer mice hibernate. House mice stay indoors year-round and breed continuously in heated space, while deer mice migrate in from fields, woodpiles, and sheds into garages, crawlspaces, attics, and wall voids, caching seeds to survive. Nests cluster in wall voids, attics, basements, and stored boxes, usually within about 30 feet of a food source.
Spring exit
Some deer mice head back outdoors as it warms in spring (March–April); house mice with an established indoor food source typically stay year-round.

Season by season

A year in the life

Mouse behavior in New Hampshire follows two overlapping cycles — an outdoor summer population boom and an indoor fall-winter surge — but neither species ever truly goes dormant.

01
Spring
House mice keep breeding indoors through early spring while deer mice head back outdoors as temperatures rise. This is the best window to seal entry points before outdoor populations expand for summer.
02
Summer
Outdoor field and deer-mouse populations peak in June and July. House mice persist indoors year-round, but home-entry pressure is comparatively low, making summer a good time to finish exclusion work before fall.
03
Fall
The highest-risk season for homeowners. Falling temperatures and vanishing outdoor food drive the indoor entry surge, peaking around the mid-to-late-October frost. Seal any gap of a ¼ inch or larger now.
04
Winter
Mice are concentrated indoors and active every night. Because house mice keep breeding in heated space, a small fall intrusion often becomes a visible infestation by midwinter — the season homeowners most often first notice mice.

New Hampshire context

Mice in southern New Hampshire

House mice are the dominant indoor mouse in Manchester, Nashua, and Concord, while deer and white-footed mice dominate rural and wooded properties and are the ones that surge indoors each fall. New Hampshire's long, cold winters make heated homes essential to survival, which is why indoor mouse activity peaks exactly when the weather turns.

Key local data

First hard frost in Manchester averages October 19 (50% probability), the tipping point for fall mouse migration indoors — NOAA 1991–2020.

We serve these communities

ManchesterNashuaConcordDerryBedfordSalemHudsonAmherst

Merrimack, Rockingham, and Hillsborough Counties

NH-licensed applicator · #782664
Same-day service
Family-owned since 2017

Service Area Map

Southern New Hampshire

When to act

Timing your treatment

Because house mice breed year-round indoors and can squeeze through a gap as small as a quarter inch, the cheapest fix is sealing up before the fall surge — but any active sign warrants prompt action.

The right window

Seal entry points (any gap ≥¼ inch) before mid-October, ahead of the frost-driven indoor migration.

Nighttime scratching, scurrying, or squeaking in walls or ceilings

Droppings (rice-grain size, dark) along walls, in cabinets, or drawers

Gnaw marks or nesting material such as shredded paper or insulation

DIY trapping hasn't resolved activity within about two weeks

An attic infestation needing cleanup, or deer-mouse droppings needing hantavirus-safe remediation

Rodent Control

Free inspection and same-day rodent service across southern New Hampshire. NH-licensed #782664.

Get a Free Inspection (603) 785-0118

Learn more about this pest

Common Questions

Frequently asked

Sources & references

CDC — Hantavirus
deer-mouse hantavirus, dried-dropping aerosol risk, safe cleanup
UNH Cooperative Extension — How Can I Get Rid of the Mice in My House?
mice nocturnal, fall entry, seal ¼-inch gaps, no winter dormancy
University of California IPM — House Mouse
home range ~30 ft, trap spacing ~10 ft, nocturnal activity, year-round breeding
CDC — Rodents
nocturnal behavior, daytime-sighting indicates larger population
NOAA NCEI — Freeze/Frost data (NH 1991–2020)
Manchester first hard frost ~Oct 19
NOAA/NWS Gray, ME — Experimental Frost/Freeze Program
Merrimack Valley growing-season end Oct 11, corroborates frost window
PestWorld — Deer Mice
deer mouse identification, seasonal indoor movement, seed caching

Editorial disclaimer: This content is provided for informational purposes only and does not constitute pest control advice. Every property is unique — consult a licensed professional for guidance specific to your situation. Anchor Pest Services is licensed in New Hampshire (#782664).

Written & reviewed by

Verified

Daniel Brady

NH-Licensed Pesticide Applicator · License #782664 (NHDAMF, RSA 430)

Daniel Brady is the New Hampshire–licensed applicator behind Anchor Pest Services, a family-owned pest control company serving the Manchester area since 2017.

Verify license

Last updated Jul 2026

Anchor Pest Services

Whatever the season — we handle the timing for you.

Same-day service across Southern New Hampshire. NH-licensed #782664, family-owned since 2017. We track the local calendar so you don't have to guess the right window.

Get a Free Inspection (603) 785-0118

NH-licensed applicator
Same-day service
Pet & family-conscious

NH License #782664 · No obligation · We answer in person

Keep Exploring

Where Do Mice Go in the Winter? NH Mouse Timing Guide

The short of it

When are they active — the whole year at a glance

What time of day are they active?

Winter behavior

A year in the life

Spring

Summer

Fall

Winter

Mice in southern New Hampshire

Timing your treatment

Frequently asked

Sources & references

Whatever the season — we handle the timing for you.

Your next step

How to Use the Jawz Plastic Mouse Trap by JT Eaton

House Mouse in New Hampshire — ID, Signs & Control

When Are Rats Most Active? NH Rat Timing Guide

Where Do Squirrels Go in the Winter? NH Timing Guide

House Mouse in New Hampshire — ID, Signs & Control

Deer Mouse in New Hampshire — Hantavirus & Safe Cleanup

Where Do Mice Go in the Winter? NH Mouse Timing Guide

The short of it

When are they active — the whole year at a glance

What time of day are they active?

Winter behavior

A year in the life

Spring

Summer

Fall

Winter

Mice in southern New Hampshire

Timing your treatment

Frequently asked