The short version
Around Great Falls, flies are busiest from about May through September. Find their source: trash, drains, compost or a dead animal. Remove it, then seal gaps and screens.
- Flies breed in something nearby.
- Check trash, drains and compost first.
- Tape a drain overnight to test it.
- Big shiny flies can mean a dead animal.
- Screens and door sweeps keep them out.
Anyone in Great Falls who wants flies out of the house.
What to look for
Flies don't come from nowhere. They breed in something nearby. In summer heat, eggs become adults in about a week. Spraying the flies you see won't stop new ones.
- 1Flies gathering at sunny windows.
- 2Tiny fuzzy flies near sinks and drains.
- 3Shiny green or blue flies indoors.
- 4Maggots in trash bins.
- 5Flies around compost or pet waste.
- 6A sudden bad smell with flies.
Why it’s worth acting soon
- Flies carry germs onto food and counters.
- Populations grow fast in warm weather.
- A dead animal smell gets worse.
- Cluster flies return every fall.
Treatment options and typical costs
Source Inspection and Fly Identification
$75–$200
A fly job starts with identification. Each fly has a different source. The technician then hunts for breeding material, not adults.
- Time
- 45–90 minutes
- Best for
- Every job; the species points to the breeding site
Exclusion: Screens, Door Sweeps and Air Curtains
$150–$450 (air curtains more)
For a home, that means tight screens and door sweeps. It is simple work with a long payoff.
- Time
- 1–4 hours
- Best for
- Buildings with steady fly entry from outside
Light Traps, Baits and Residual Resting-Surface Treatment
$150–$450
For a Great Falls restaurant, discreet wall-mounted light traps near the kitchen and prep areas are common. Bright zappers near the front door attract more flies.
- Time
- 1–2 hours
- Best for
- Knocking down adults while sources are fixed
Cluster-Fly Void Treatment, Sealing and Follow-Up Monitoring
$150–$500; follow-ups $50–$150
A good follow-up in Great Falls is short and specific. The tech checks activity is down and adjusts placements.
- Time
- 1–3 hours, plus scheduled checks
- Best for
- Cluster flies each fall; ongoing checks for commercial sites
Prices are typical published ranges. Ask what’s included before you compare quotes.
Cluster flies spend the winter in attics and wall voids, then come out on warm days.Which flies show up around Great Falls.
They show up at windows on warm days. Fungus gnats hover around overwatered houseplants. House flies are the most common around Great Falls. They breed in trash, compost and manure. Drain flies are tiny and fuzzy. They breed in the slime inside drains. Blow flies are shiny green or blue. A sudden swarm often means something died nearby. Cluster flies hide in attics and walls around Great Falls for winter.
Local flies conditions in Great Falls.
Knowing Great Falls's seasonal timing lets you schedule treatment before the busy stretch rather than after it, which usually means faster service and a more accurate quote. A provider who works Great Falls and Montana every day can point out the specific conditions that matter most here, and getting the scope, price, and follow-up terms in writing makes it easier to compare options. Great Falls sits in a semi-arid continental climate, and that sets the pace for fly activity here: spring through fall; cluster flies overwinter indoors. In Great Falls, the area is mostly suburban, so flies pressure can differ from one block to the next depending on how tight the entry points are and how much food, water, or shelter is close by. An inspection in Great Falls usually starts outside and works inward, checking the foundation, gaps around doors and windows, and any moisture or clutter near the structure first.
Trash bins are the top source in summer. Keep lids closed and rinse bins every week or two.Fly season in Great Falls.
Seal gaps before September. The season is short but busy. Cluster flies move into walls in fall.
Finding the source.
Likely a dead animal. Around Great Falls, trash bins in summer are the usual culprit. Watch where flies gather and where they're coming from. Check trash bins, recycling and compost first. Tape over a drain overnight. Flies stuck to it mean the drain is the source. Bad smell plus big shiny flies?
A year of flies in Great Falls.
- Summer: peak season in Great Falls. Empty trash often. - Fall: cluster flies move into walls. Seal gaps early. - Winter: cluster flies appear at windows on warm days. - Spring: flies return in May.
Which fly is it?
- Drain fly: tiny, fuzzy, moth-like wings. - Blow fly: shiny green, blue or bronze. - Cluster fly: big, slow, golden hairs. - Fungus gnat: tiny and black, near plants. - Fruit fly: tan with red eyes, near ripe fruit. - House fly: gray, a quarter inch, everywhere.
Cleaning a drain fly drain.
- Enzyme: pour in an enzyme drain cleaner at night. - Repeat: do it daily for a week. - Check: tape over the drain to see if flies still emerge. - Skip: bleach alone doesn’t clear the slime. - Scrub: run a stiff brush down the drain.
Keeping flies out.
- Sweeps: add door sweeps to exterior doors. - Trash: keep lids closed and rinse bins. - Compost: cover it and keep it away from doors. - Pets: pick up waste daily. - Screens: patch holes in windows and doors.
Fly traps that actually help.
- UV light traps: best for kitchens and businesses. - Bait traps: hang them outside, away from doors. - Swatter: still works for a few strays. - Skip: bug bombs. They don’t reach the source. - Sticky ribbons: fine for garages and sheds.
If something died nearby.
A wall may need a small hole opened. The flies stop once the source is gone. Follow the smell and the flies. Wear gloves, bag it, and disinfect the spot.
Flies and pets.
Pet food and waste draw flies fast. Pick up food bowls after meals. Clean up the yard daily in summer. Flies biting a dog's ears are usually stable flies. Ask your vet about protection.
Flies at a business.
Use air curtains or strip doors at busy entries. Schedule drain cleaning and regular service visits. Restaurants and food businesses need a steady routine. Seal dumpsters and clean them weekly.
Flies and food safety.
Throw out food flies have landed on for long. Keep fruit in the fridge in summer. Flies land on trash and then on food. Cover food outdoors and wipe counters often.
What a fly visit looks like.
Then they clean, seal or treat what they find. Traps help confirm the problem is gone. The tech looks for the source first. They check trash areas, drains, attics and gaps by doors.
Screens and doors.
- Doors: add sweeps and keep them closed. - Patio doors: a screen door helps in summer. - Fans: a fan by the door keeps flies moving on. - Screens: patch holes and check the corners.
Compost and yard waste.
Bag clippings. Pick up fruit and pet waste every few days. Flies breed in wet, rotting material. Keep compost covered and turn it often.
Trash day habits.
Keep lids shut and park bins away from doors. Bag food scraps tightly before they go in the bin. Rinse bins every couple of weeks in warm weather.
Questions to ask before you sign.
- Where are they breeding? - What will you clean, seal or treat? - Are follow-up visits included? - Is dead animal removal extra? - What kind of fly is it?
What affects the price
- Size of the building and attic for cluster flies.
- One-time visit versus monthly service plan.
- Number of breeding sources found.
- Plumbing repairs for slow drains or broken lines.
- Follow-up visits and monitor replacement.
- Air curtain installation for commercial doors.
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What bothers you most about flies?
When to call for help
Businesses usually need regular service. if cluster flies come back every fall. if you smell something dead in a wall. Call if you can't find the source after a few days.
What you can do yourself
A pro helps with hidden sources, walls and attics. Clean drains, rinse bins and fix screens. Find the source and remove it. Most home fly problems are DIY.
Flies in Great Falls
With about 14 inches of rain a year, damp spots around Great Falls also breed small flies. In Great Falls's neighborhoods, the usual sources are trash bins, compost, pet waste and drains. Summer highs near 85°F in Great Falls speed up the fly life cycle, so trash and compost need extra care.
Fly tips from the experts
Where are the flies coming from?
The kind of fly tells you where to look. Around Great Falls, Montana, note its size, where it gathers and when it shows up. Then go after the source.
Small flies near drains
Tiny, fuzzy flies near a sink or shower usually breed in the slimy film inside the drain. Scrub the drain with a stiff brush. Spraying the adults won’t stop them.
UC IPM: drain fliesHouse flies around doors and trash
House flies breed in garbage, pet waste and rotting plants. Clear those out first, then add screens and keep doors closed. Traps help, but they don’t fix the source.
EPA: managing fliesSlow flies at the windows in fall?
In colder states like Montana, sluggish flies at upstairs windows in fall, winter or early spring are often cluster flies. They spend winter in attics and walls but don’t breed indoors. Sealing gaps outside in late summer keeps them out.
University of Minnesota Extension: fliesBased on guidance from university extension services and the EPA.
How we check our sourcesLocal research
Flies in Great Falls, MT: what the public record shows
Before you compare quotes, it helps to know which flies actually live in Montana, when they are busiest around Great Falls, and what the state figures look like. Everything below links to the agency or university page it came from.
Face flies overwinter inside Montana structures
Montana homeowners who find flies in the house during a winter warm spell are usually dealing with face flies that entered the attic the previous fall.
Montana State University ExtensionFace fly life cycle and egg output
Because face flies breed in undisturbed pasture manure rather than confined manure piles, manure removal will not solve a Montana face fly problem the way it solves a house fly problem.
Montana State University ExtensionFace fly infestation threshold on cattle
It gives Montana livestock owners a countable trigger for treatment rather than a subjective judgment about whether flies look bad.
Montana State University ExtensionFly species recorded in Montana
- House fly (Musca domestica) — Non-biting; breeds in manure, garbage, lawn clippings, decaying produce. 45 days at 60°F to 7 days at 95°F. Carries bacteria and viruses causing diarrhea, cholera, food poisonin…
- Stable fly (Stomoxys calcitrans) — Biting fly with bayonet-like proboscis; about 12 days egg to adult; peaks early summer.
When flies are busiest around Great Falls
MSU Extension describes face flies as active on livestock through the warm summer months, then entering attics, barns and sheds in the fall to overwinter as adults, with nuisance appearances indoors during winter warm spells.
MSU Extension notes that stable fly larvae develop in decaying organic matter such as wet hay and winter feeding areas, so cleaning up wet hay residue is the practical control step on Montana properties.
Sources: Montana State University Extension; Texas A&M AgriLife Extension; University of New Hampshire Extension; Flies (Home and Landscape). Figures are quoted as the source prints them. How we check our sources
Simple ways to keep flies away
- Keep trash bins closed and rinse them.
- Take trash out often in summer.
- Repair window and door screens.
- Add door sweeps.
- Pick up pet waste daily.
- Clean drains with a brush and enzyme cleaner.
A good quote names the fly, the source, and what will be cleaned, sealed or treated.Did you know?
Drain flies are sometimes called moth flies
Phorid flies prefer running to flying
Questions people ask
Why do I get flies in a clean house?
There's often a hidden source, like a drain or trash bin.
How do professionals get rid of flies?
They find the source first. Then cleaning, sealing, traps and, if needed, a targeted treatment.
What are cluster flies and why are they in my attic?
They're large, slow flies that winter in walls and attics. They come out on warm days and gather at windows.
How long does professional fly control take to work?
Usually days, once the source is removed. Cluster flies take a season of sealing.
How do I get rid of drain flies for good?
Repeat for a week. Bleach alone won't do it. Scrub the drain with a stiff brush. Then use an enzyme cleaner.
Are drain flies common in houses?
In Great Falls, flies are controlled by finding and removing the breeding source — the garbage, food, or moisture they are drawn to. In Great Falls, cleaning the source and setting traps handles the adults, and because flies reproduce quickly, source removal is the part that actually stops them.
What are the tiny black flies around my houseplants?
In Great Falls, ninety-six percent of 50 North Carolina homes in a 2012 study had dark-winged fungus gnats, the tiny flies that breed in damp potting soil.
Are cluster flies common in Great Falls?
Yes, they're a fall and winter nuisance around Great Falls. Seal gaps around windows and siding before September.
When is fly season in Great Falls?
Flies are busiest from about May through September. Cluster flies also appear at windows in winter.
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Sources (12)
The facts in this article come from the public sources listed above. Every home is different, so ask the company you talk to about pricing and what’s included. Published by Fly Exterminator · Updated September 11, 2026 · How we write these guides