Why Rats and Mice Move In When the Rains Come Back

A wetland pond with cattails beside a split-rail fence at the Tualatin Hills Nature Park in Beaverton — Wetlands at the Tualatin Hills Nature Park. Beaverton grew up on low, wet ground.

Every fall, some Beaverton homeowners hear their first scratching in the wall within a few weeks of the rains coming back. The timing lines up for a reason. This guide explains what's going on and what to check before October.

What the Weather Does

Beaverton averages about 39 inches of precipitation a year over roughly 150 days. When the rain returns after summer, burrows along fences and foundations get wet and rats and mice look for dry, sheltered spots. A crawl space, a garage or the gap behind a stack of firewood all qualify.

A Late-Summer Checklist

Do these in August or September while it's dry:

Walk the foundation and check every crawl space vent screen
Look at the garage door seal, especially the corners
Check the dryer vent flap and the holes where pipes leave the house
Stack firewood off the ground and away from the siding
Cut blackberry and ivy back from the house and fence
Move bird feeders away from the house and clean up spilled seed

Signs They've Already Moved In

Scratching under the floor or in the walls at night, droppings in the garage or under the sink, chewed boxes, and a musty smell from the crawl space hatch. If you see those, call before they settle in. See mouse control and rat control.

Questions People Ask

Is it too late if it's already November?

No. Trapping and sealing work any time of year. The dry months are just easier for outside work.