No: a mouse has almost no defence against outdoor seasons
A fancy mouse cannot live outdoors all year round in a hutch or run, because its tiny body cannot regulate against what a hutch lets in. A cold night that merely cools a rabbit can drop a mouse into fatal torpor, damp bedding accelerates the heat loss, and a hutch warming in direct sun can overheat mice before anyone notices the day has turned hot. Mice in the wild survive winters deep in insulated nests with a colony's shared warmth and stored food; a hutch colony gets the exposure without those deep-burrow defences. Indoors, the temperature band a mouse needs is simply the band a home already holds.
Outdoor housing surrounds mice with things that hunt or infect them
A fancy mouse kept outdoors spends its life within scent of cats, rats, owls, and foxes, and a hutch gives it nowhere to flee from that awareness. Wild mice and rats can reach a hutch's occupants through mesh or shared food, bringing parasites and diseases that a fancy colony has no resistance built against, and a wild male getting in can mean fighting and unwanted litters. Insects, slugs fouling food, and rain washing through bedding all pile onto animals that groom constantly and ingest whatever is on their coats. A hutch cannot be made sterile; a room, effectively, can be kept clean enough.
Hutch and run construction loses to a mouse every time
Even the containment fails for a fancy mouse outdoors. Hutches are built to rabbit tolerances: gaps at door corners, chewable wood, and mesh wide enough for a mouse to slip through or be pulled through are normal features. A run on grass parts from the soil as the ground shifts, opening ground-level exits a mouse will test and find, and once a fancy mouse is out in a garden it is gone, to predation or exposure, within a very short time. Mice are also relentless chewers with teeth that never stop growing, so wooden hutch walls are a project to them, not a boundary.
The right home for fancy mice is indoors and interesting
A fancy mouse colony indoors can have everything a hutch promises, without the lethal parts: a roomy glass or solid-sided enclosure with a fastened mesh lid for air, deep bedding to dig and tunnel in, nesting material they shred into proper beds, wheels, ropes, and cardboard that is replaced as they destroy it. Females grouped together supply the social warmth a wild colony gets from its pile, and a steady room temperature removes the seasonal gamble entirely. Put the enclosure somewhere calm, out of direct sun and away from radiators, and the mice will be active, curious, and long-lived by mouse standards.
If mice have been kept outside, move them in and watch them
Fancy mice currently living in a hutch or shed should be brought indoors without waiting for bad weather to make the decision urgent. Set up the indoor enclosure first, transfer some of their used bedding and nest material so the new home smells familiar, and move the whole group together to keep the colony intact. Over the following days, check that all of them are eating, active at dusk, and breathing quietly; sneezing, hunched postures, or a mouse sitting apart from the pile after time outdoors warrants a vet visit. KinsLe's Care Teams lets you assign your fancy mice's feeding, water, and bedding checks to family or helpers with timestamps on each task, so the colony's indoor routine stays dependable.