Biting flies on the beach.
I come to the Cape every year for the past 13 years so I am familiar with most things. The question I have is simply how bad or not are the biting flies this summer?
I will be up there right after Labor day. Those flies sure can ruin the day.
I live in NJ so we get nasty greenheads!! If the wind is coming out of the west I stay away from the beach. Can the same thing be applied on the Cape?
Yes — the biting-fly situation on Cape Cod (including around Wellfleet) each summer can indeed be a serious nuisance — especially if you’re used to dealing with biting flies (like greenheads) back in New Jersey. What you experience will depend a lot on timing, tide, wind, and how close the beach is to marshy areas, but here’s what you should know based on the latest information and local reports.
How bad are the flies this year — and what you should expect just after Labor Day
On Cape Cod, the main biting nuisance on beaches near salt-marshes are Greenhead fly (a salt-marsh horse fly species). Their adult season runs roughly from late June to mid-August, with peak abundance in July and early August.
By the time you arrive (just after Labor Day), greenhead numbers usually drop significantly. According to regional control-efforts data, the greenheads — which are strongly tied to marshes — begin to taper off in late August or early September as conditions change.
That said — it’s not guaranteed you’ll avoid all biting flies. The marshy coastlines of Cape Cod also tend to harbor mosquitoes and possibly smaller biting midges (depending on tide, vegetation, and water conditions), especially in late summer.
So, in many years your timing (just after Labor Day) works in your favor — you may see fewer greenheads, but some biting insects could still be around.
What makes fly-bother fluctuate — and when it’s most likely bad
- Proximity to marshes/salt-marsh grasses: Beaches and dunes near marshes are hot zones for greenheads and other salt-marish biting rigs. If your rental and chosen beach are near marshland or wetlands, expect higher risk.
- Wind conditions matter a lot: Greenheads and similar biting flies hate strong breezes — when there’s wind off the ocean or bay, they struggle to fly, so windy days tend to be much more pleasant and “fly-free.” This is a major factor on Cape, similar to your experience at NJ beaches.
- Timing within day: Unlike mosquitoes that bite at dusk/dawn, many marsh-associated flies (including greenheads) are active during the day when they search for blood meals.
- Seasonality — by September it usually calms down: Historically, fly populations drop significantly by late August/early September, so your visit just after Labor Day tends to coincide with a calmer period.
What many Cape-goers do to minimize bites — good “Cape-Cape Cod” tips (especially useful if you come from a place like NJ)
- Check the wind before you head to the beach: Strong breezes (offshore or along the coast) make a big difference — windy beaches tend to have far fewer biting flies than calm marsh-adjacent ones. Many locals avoid marsh-side beaches when wind is light.
- Wear light-colored and looser clothing: Biting flies tend to be attracted to darker colors and sweat/skin scent. Light clothes, long sleeves/pants, and socks help deter them.
- Use a good insect repellent: Repellents with DEET or proven formulations (some local “Cape Cod” repellents are designed for greenheads) are often helpful.
- Avoid marsh-edge / tall-grass areas: Marsh grasses are breeding grounds and resting spots — staying away from them when you can reduces encounters.
- Plan beach time around tides and water exposure: Some people report greenheads (and other biting flies) being less aggressive when you are wet or right after swimming, because they are attracted to salt/sweat — so timing your beach visit to swim first, dry off quickly or stay near water may help.
Bottom line — what to expect this summer and whether your NJ “greenhead-avoidance habits” hold up on the Cape
Yes — your instincts from NJ are valid on Cape Cod. Beaches and marsh-adjacent areas of Cape tend to harbor biting salt-marsh flies (greenheads) and sometimes mosquitoes, especially earlier in summer. But since your trip is just after Labor Day, past the peak season, the risk is usually lower — especially if you pick beach days with wind and avoid marsh-edge zones.
Still, there’s no guarantee you’ll be 100% bite-free. Packing some good insect repellent, wearing protective clothing, and paying attention to wind/tide/weather will give you the best chance of a comfortable beach week.
