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There's nothing quite like cracking open a window on a warm summer day - until the flies show up uninvited. One minute you're enjoying the breeze; the next, you're swatting at a buzzing intruder dive-bombing your fruit bowl.
If you're constantly battling flies indoors, you're not alone. Summer is peak season for houseflies, fruit flies, and blowflies, and once they're in, they're annoyingly hard to shift. The good news? Keeping flies out of your house doesn't require toxic sprays or a full-scale fumigation. It just takes the right strategy.
In this guide, we'll walk you through exactly how to keep flies out of your house in summer - from blocking their entry points to making your home genuinely unappealing to them in the first place.
Why Are There So Many Flies in Summer?
Before you can stop flies from coming in, it helps to understand why summer draws them inside in the first place.
Flies are cold-blooded, which means they thrive in warm temperatures. As outdoor temperatures rise, fly populations explode - a single housefly can lay up to 500 eggs in her lifetime, and those eggs hatch in as little as 12 hours in warm conditions. More flies outside means more pressure on your home.
They're also driven indoors by exactly what you've got:
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Food - even crumbs, residue on dishes, or open bins
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Moisture - damp sponges, standing water, leaky pipes
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Warmth - your home is a comfortable refuge from the midday heat
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Light - flies are attracted to bright, lit spaces at dusk
Understanding this means your fly prevention strategy needs to work on multiple fronts: block entry, eliminate attraction, and disrupt their breeding cycle.
How to Keep Flies Out of Your House: 10 Proven Methods
1. Seal Every Entry Point
The most effective long-term fly prevention is making it physically impossible for flies to get in. Flies are tiny - they don't need much of a gap.
Check and fix these common entry points:
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Windows and doors: Install fine-mesh fly screens on all windows you open regularly. For doors, use a magnetic fly screen curtain or a door draft excluder at the base. You can also use Outdoor Fly Bag Trap to prevent them from coming inside.
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Gaps around pipes and vents: Use silicone sealant to close small gaps where flies can squeeze through.
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Roof vents and extractor fans: Add fly mesh behind vent covers to block access while maintaining airflow.
This is your first and most important line of defence. No gap - no flies.
2. Remove What's Attracting Them
Flies don't enter your home for a holiday. They're after food, water, and a place to breed. Remove those, and you remove the incentive.
In the kitchen:
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Store fruit in the fridge during summer, not in a bowl on the counter
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Never leave dirty dishes sitting out - even for an hour
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Wipe down surfaces after cooking, especially around the hob and sink
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Empty your indoor bin daily, or at least every two days
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Use a bin with a tight-fitting lid and clean it regularly with a diluted bleach solution
In the bathroom:
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Don't leave damp towels or sponges sitting on surfaces
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Fix dripping taps - standing water is a breeding site
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Clean drains regularly, as organic matter can build up and attract drain flies
In the garden:
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Don't leave pet waste sitting on the lawn
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Keep outdoor bins sealed and away from the back door
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Turn your compost heap regularly and keep it covered
3. Use Natural Fly Repellents Around the Home
If you'd rather not reach for chemical sprays - especially in a home with kids or pets - natural fly repellents are highly effective and smell far better.
Essential oils flies hate:
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Lavender - Place dried lavender bunches near windows or use a lavender essential oil diffuser
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Peppermint - Flies strongly dislike the menthol scent; dab diluted peppermint oil on windowsills and door frames
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Eucalyptus - Works similarly to peppermint and doubles as a pleasant room fragrance
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Cloves - Studding an orange with cloves and leaving it on a countertop is a classic, effective deterrent
Grow fly-repelling herbs on your windowsill:
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Basil
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Mint
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Rosemary
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Bay leaves
This gives you a dual function: culinary herbs at arm's reach and a natural fly barrier.
4. Set Up Strategic Fly Traps
Even with good prevention, a few flies will inevitably make it inside. Traps are your backup line of defence.
Options that work well:
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Apple cider vinegar traps - Pour a small amount into a glass, add a drop of dish soap, cover with cling film, and pierce small holes. Leave near fruit bowls or bins.
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Sticky fly paper - Old-fashioned but undeniably effective. Use Catchmaster’s XL Window Fly Traps, Hang it away from food prep areas.
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UV light plug in Flying Insect Trap - A UV light lures flies in and eliminates them. Ideal for kitchens or utility rooms. [Link to product here]
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Window fly traps - Adhesive strips that fix to the inside of windows to catch flies attracted to natural light.
5. Keep Your Bins Under Control
Bins are fly magnet number one. Both indoor and outdoor bins need year-round management, but especially in summer when heat accelerates decomposition.
Indoor bin tips:
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Use a pedal bin with a sealed lid - avoid open-top bins entirely in summer
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Line your bin with compostable bags and take it out every 1-2 days
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Rinse food packaging before binning - milk cartons and meat trays are major attractors
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Sprinkle bicarbonate of soda at the base to neutralise odours
Outdoor bin tips:
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Keep bins in a shaded area - heat speeds up decomposition
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Rinse bins monthly with hot water and diluted disinfectant
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Never leave bin lids open, even briefly
Pair your prevention routine with a UV fly killer for fast backup control in kitchens and utility rooms.
6. Be Smart About How You Ventilate Your Home
Summer ventilation and fly prevention can feel like opposing goals. The answer is working smarter with airflow.
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Open windows on the shaded side of your home - flies are less active in cooler spots
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Use fly screens - a fine mesh screen lets the breeze in and keeps insects out
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Use fans strategically - flies struggle to navigate in consistent airflow. A box fan near an open door creates a wind barrier
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Close windows at dusk - flies are drawn to lit, warm interiors in the evening
7. Address Drain Flies Separately
If you're seeing tiny flies clustering around your sink, shower, or bathroom drain, you may have drain flies - they breed in the organic sludge inside pipes.
How to get rid of drain flies:
- Pour boiling water down affected drains twice a day for a week
- Use a long drain brush to scrub the inside of the pipe
- Pour a mixture of baking soda and white vinegar down the drain, leave for 30 minutes, then flush with hot water
- Use a dedicated drain cleaner gel to break down organic buildup
8. Try a Fly Repellent Spray for Entry Points
A targeted fly repellent spray applied around doors and windowsills creates a barrier that deters flies from crossing the threshold. Look for products containing permethrin or a plant-based alternative like citronella or pyrethrin.
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Spray around door and window frames, not inside your living space
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Reapply every 2-4 weeks or after rain
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Pay attention to the back door, especially if you have pets or a garden nearby
9. Clean Your Kitchen More Regularly Than You Think You Need To
You might keep a clean kitchen - but fly-level clean requires a little more attention during summer months.
The fly-prevention kitchen cleaning routine:
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Daily: Wipe countertops, wash dishes, empty the bin, sweep crumbs
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Every 2-3 days: Clean the hob, wipe the microwave, take out food waste
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Weekly: Deep-clean the bin, mop the floor, check for forgotten food in cupboards
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Monthly: Clean behind the fridge and cooker, check for hidden damp
10. Make Your Outdoor Space Less Fly-Friendly
What happens in your garden directly impacts how many flies make it into your house.
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Remove standing water from plant saucers, water features, and blocked gutters
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Keep outdoor food covered during BBQs and garden meals
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Clean pet bowls and feeding areas after every use
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Compost correctly - a well-maintained compost bin shouldn't attract flies
Quick-Reference Summary Table
|
Method |
Best For |
Cost |
|
Fly screens on windows |
Ongoing prevention |
Low |
|
Sealed bins with lids |
Removing attractants |
Low |
|
Natural herb repellents |
Kitchen / windowsill |
Very low |
|
Apple cider vinegar traps |
Fruit flies |
Very low |
|
UV fly killer |
Kitchen / utility room |
Medium |
|
Door draught excluders |
Entry point sealing |
Low |
|
Repellent spray on frames |
External entry points |
Low |
|
Fan at entry doors |
Ventilation without flies |
Low |
When to Call a Professional
If you've tried the above and you're still dealing with large numbers of flies indoors, it may point to a more serious issue - such as a dead animal in the roof space or a hidden drain blockage.
Signs it's time to call pest control:
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Sudden appearance of dozens of flies in a specific room
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Flies appearing consistently in one spot despite cleaning
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Presence of maggots - indicating an active breeding site nearby
Conclusion
Keeping flies out of your house in summer is absolutely achievable - it just requires a layered approach. Block their entry, remove what attracts them, disrupt their breeding cycle, and use repellents and traps as backup. Do all of those things consistently, and you'll enjoy an open-window summer without the constant swatting.
The key is not waiting until you have a fly problem to act. Set up your screens, clean your bins, and get your natural repellents in place before summer peaks - and you'll stay one step ahead all season long.
Frequently Asked Questions
Q: Why do flies come inside more in summer?
Flies are cold-blooded and their populations explode as outdoor temperatures rise. Warmth, food, moisture, and light draw them toward open windows and doors more often in summer than any other season.
Q: Do fly screens really work?
Yes. A fine-mesh screen fitted flush to windows and doors is one of the most effective long-term barriers, since it lets airflow in while physically blocking flies from entering.
Q: What's the fastest way to get rid of flies without chemicals?
Combine an apple cider vinegar trap or sticky fly paper with a thorough clean of kitchen surfaces, bins, and drains. Removing the food or breeding source alongside trapping active flies gives the fastest results.
Q: Are natural fly repellents like essential oils safe around pets?
Generally yes in diluted form, but some essential oils (including tea tree and certain concentrated citrus oils) can be harmful to cats in particular. Always check pet-safety guidance for the specific oil before diffusing or spraying it around pets.
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