Living in Colorado means enjoying all four seasons, from snowy winters to colorful spring blooms, warm summer days, and crisp autumn evenings. Each season brings something to love, but it also affects the pests in and around our homes. While many pests only show up at certain times of the year, mice are different. No matter the season, these little intruders can be a problem in Colorado homes.

EnviroPest has been helping Denver, Colorado Springs, and Northern Colorado homeowners deal with mice for over 50 years. During that time, we’ve learned much about how seasonal changes affect mouse activity and how to stay ahead of them. Here’s what you should know about mice each season, and the steps you can take to avoid an infestation.

house mouse near denver home

Season-by-Season Behavior of Mice in Colorado

Spring

As the weather warms up and food sources reappear, mice become more active in spring. Although they can breed throughout the year, spring usually brings a surge in population growth. You may notice increased mouse activity around your yard or even inside your home as they forage for food and nesting materials.

Summer

Summer provides mice with plenty of natural food sources—plants, seeds, and insects are all abundant. During these months, they’re often more active outdoors. However, don’t be fooled into thinking summer means you’re safe. Mice may still take shelter indoors if they find reliable food or outdoor conditions become too hot or dry.

Fall

Fall is when mice's activity spikes indoors. As temperatures cool and food becomes scarce outdoors, they start looking for warm, sheltered places with steady access to food and water. For many Colorado homeowners, this is when infestations begin. Spotting one mouse often means more are nearby since mice are social animals and multiply quickly.

Winter

By the time winter sets in, most mice have already moved inside. You may not see them outdoors, but that doesn’t mean they’ve disappeared. Once indoors, they stay active all winter, raiding kitchens, contaminating food, and chewing through materials to keep their nests comfortable.

Why Fall Is the Worst for Mice in Colorado

While mice can be a problem year-round, homeowners see the most infestations begin in fall. Cooler nights drive them to seek out cozy spaces, and homes provide everything they want and need to survive: warmth, food, and shelter. If mice find a way inside, establishing a colony usually doesn’t take long. Left unchecked, a small problem in September can become big by the time winter is in full swing.

Homeowner Rodent Prevention Checklist

The best way to avoid dealing with mice is to make your home less inviting and harder to access. A two-part prevention strategy works best: keep them out and remove what attracts them. Use this checklist to protect your home:

  • Seal every gap and crack—even tiny holes matter. Mice can squeeze through openings the size of a dime.
  • Replace or repair damaged weather stripping, vent covers, and window screens.
  • Declutter storage spaces like basements, garages, and attics.
  • Keep firewood stacked off the ground and away from your home.
  • Store food in sealed containers and clean up crumbs and spills promptly.
  • Clear away yard debris, including fallen leaves and branches.
  • Trim shrubs, plants, and tree branches so they don’t touch your home.
  • Reduce excess moisture indoors and out.
  • Eliminate standing water, and make sure gutters and downspouts are clear.

Why Choose EnviroPest This Fall (and Beyond)

Preventing mice before they settle in is always easier and less costly than removing a full infestation. That’s where EnviroPest can help. Our home pest control plan stops rodents and other pests before they become a problem, protecting your home year-round.

Our Colorado’s Choice Smart Service includes:

  • Protection against 30+ common pests, including mice
  • Four seasonal service visits targeting pests specific to each season
  • 24/7 digital rodent monitoring for early detection
  • Free re-treatments if pests return

With EnviroPest on your side, you don’t have to wait until mice show up to take action. Our proactive approach protects your home before infestations have a chance to develop.

Since 1965, homeowners across Denver, Colorado Springs, and Northern Colorado have trusted EnviroPest for expert pest control. Our local experience means we know the unique challenges Colorado homeowners face and how to solve them.

If you’re ready to keep mice out this fall and all year, contact us today for an estimate. Ask about our Enviro Guard exclusion program for even stronger rodent protection. With EnviroPest, your home is in good hands.