February 27, 2026 Anthony Gatto

What temperature is too hot for a fly sheet?

If you're reading this, you're probably staring at the weather forecast and wondering whether to leave your horse's fly sheet on or pull it off before the afternoon heat hits. It's a common dilemma. You want to protect your horse from biting insects, but you don't want to risk overheating.

Here's the good news: fly sheets can be perfectly safe in hot weather when you choose the right material and pay attention to a few key factors. At Kensington, we've been manufacturing breathable fly protection since 1954, and we've learned that the question isn't simply "what temperature is too hot?" but rather "what conditions make a fly sheet safe or unsafe?"

Let's break down what you actually need to know.

The short answer: it's about heat index, not just temperature

If you want a simple number to remember, veterinarians generally recommend keeping horses in fly sheets when the heat index is under 90°F. Go above that threshold, and you need to start paying closer attention to your individual horse and environment.

But here's the important part: heat index is not the same as air temperature. Heat index combines temperature with humidity to measure how hot it actually feels. A 90°F day with low humidity might have a heat index of 85°F, which is generally fine. That same 90°F temperature with 80% humidity could push the heat index to 105°F, which is dangerous territory.

Dr. Erin Denney-Jones, an FEI veterinarian based in Florida, explains it this way: "I would recommend anything under 90 degrees heat index would be tolerated in a normal weight, sweating horse in the shade with a breeze or fan on them. Over 90 degrees I would recommend providing a cool environment in order for them to tolerate the blanket and heat well."

Source: TheHorse.com

The takeaway? Check your local heat index, not just the thermometer. Most weather apps display this automatically.

Six factors that determine fly sheet safety in hot weather

Temperature is just one piece of the puzzle. Here are six factors that matter just as much, if not more.

1. Heat index (temperature + humidity)

We've covered this, but it bears repeating. Humidity prevents sweat from evaporating, which is how horses cool themselves. In dry climates, horses can tolerate higher temperatures because their sweat actually works. In humid climates, the same temperature can be dangerous because sweat just sits on the coat.

A horse owner from Pennsylvania put it simply in a forum discussion: "90 and dry would be fine. 90 and Pennsylvania humid is awful!"

Source: Chronicle Forums

2. Shade availability

Shade is arguably the most important environmental factor. A horse in direct sun at 85°F is experiencing very different conditions than a horse under a shade tree at the same temperature.

Not all shade is equal:

Shade trees provide the best cooling because they block sun while allowing airflow from all directions
Run-in sheds can actually trap heat if they're not deep enough or don't have adequate ventilation
Open-sided shade structures (tilted roofs on poles) work well because they maximize both shade and airflow

If your turnout only has a run-in shed, check that it provides genuine cooling and isn't just blocking the breeze. A confined, buggy shed can be worse than no shade at all.

3. Fly sheet material and breathability

This is where your choice of fly sheet makes all the difference. Not all fly sheets breathe equally.

Materials that work well in heat:

Ripstop Nylon Mesh - lightweight with a looser weave that allows maximum airflow
Mosquito Mesh - finer weave for small insect protection, but still breathable
Textilene® - a stiff, PVC-coated mesh that stands away from the horse's body, creating natural air channels

Materials to avoid in extreme heat:

Heavy Dura-Mesh or vinyl-coated fabrics
Tight-weave materials that cling to the coat
Dark-colored sheets that absorb heat

Here's something that surprises many horse owners: a white or light-colored fly sheet can actually keep a horse cooler than no sheet at all. The light color reflects UV rays rather than letting them hit the horse's dark coat.

A horse owner from Central Florida shared this experience: "I purchased a white fly sheet about a month ago. I too was concerned about overheating esp in our climate. My bay goes out on pasture/direct sun from 8am-noon. He has always sweat this time of year. I would be very concerned if he didn't, but since turning him out with the fly sheet on, I have noticed the area not covered by the sheet (his neck) is sweaty and the area under the fly sheet (except where the girth strap lies) is dry. I can only assume the white reflects the heat."

Source: Chronicle Forums

At Kensington, our Textilene® fabric is specifically engineered for this balance: 73% UV protection with 78% air permeability. The material's stiffness creates natural airflow channels between the sheet and the horse's coat.

4. Horse color and coat

Dark bay and black horses absorb significantly more solar radiation than light-colored horses. If you've ever worn a black shirt versus a white shirt on a sunny day, you understand the difference.

A fly sheet with UV protection can actually help dark horses stay cooler by reflecting those rays before they hit the coat. Some horse owners report their dark horses are more comfortable with a white fly sheet than without one.

Conversely, horses with white coats, pink skin, or light markings need fly sheets for a different reason: sunburn protection. These horses are at risk for painful burns and skin damage without coverage.

5. Airflow and breeze

Natural breeze or fans can make a significant difference in fly sheet safety. Moving air helps evaporate sweat and prevents heat from building up under the sheet.

If your horse is stalled, fans can make fly sheets viable in temperatures that would be too hot without them. In pasture, look for locations with natural airflow rather than enclosed areas.

6. Individual horse factors

Just like people, horses have different heat tolerances:

Body condition - Overweight horses overheat more easily than fit horses
Breed - Draft horses and heavily muscled breeds generally handle heat less well than lighter breeds
Fitness level - Conditioned horses thermoregulate better than unfit horses
Acclimatization - Horses used to hot weather handle it better than those suddenly exposed

Dr. Denney-Jones notes: "A draft horse with a body condition score of 8 will have more difficulty in an environment with a heat index of 90 degrees or more compared to a light horse with a body condition score of a 5, with or without a fly sheet."

Source: TheHorse.com

Warning signs your horse is overheating

Even with the right fly sheet and good conditions, you should check your horse regularly in hot weather. Here's what to watch for:

Excessive sweating under the fly sheet - Some sweating is normal, but heavy sweating indicates the sheet may be trapping heat
Rapid breathing or panting - Horses normally breathe 8-16 times per minute; faster rates suggest heat stress
Lethargy or reluctance to move - A horse that seems unusually tired or unresponsive needs attention
Skin that feels hot to the touch - Check under the fly sheet; the skin should not feel abnormally warm

If you notice these signs, remove the fly sheet immediately, move the horse to shade, and provide cool water. In severe cases, contact your veterinarian.

Monitoring these four physical indicators helps owners decide when the heat index is too high for safe fly sheet use.

Choosing the right fly sheet for hot weather

If you live in a hot climate, your fly sheet choice matters more than the exact temperature on the thermometer. Here's what to look for:

Breathability first - Look for lightweight mesh materials with open weaves. The more air that can flow through and under the sheet, the better.

UV protection without compromise - You want UV blocking (it protects the coat and reflects heat), but not at the expense of airflow. Our Kensington Protective Fly Sheet provides 73% UV protection while maintaining high breathability.

Proper fit for ventilation - A fly sheet that's too tight restricts airflow. One that's too loose can bunch and create hot spots. The sheet should allow a hand to slide easily between the fabric and the horse's coat.

Light colors - White or light-colored sheets reflect heat. Dark sheets absorb it.

For more on why UV protection matters for horses, see our guide on the importance of UV protection for horses.

Regional considerations: climate matters

Horse owners in different climates report very different experiences with fly sheets in heat:

Dry climates (Arizona, California, Texas) - Many owners successfully use fly sheets even when temperatures exceed 100°F. The key is the low humidity. As one Texas owner noted: "My mare loves her fly sheet. It even has a neck cover. I think it actually keeps her cooler. The other horses are sweaty and she is not even though she usually sweats more than the others."

Source: Barrel Horse World Forums

Humid climates (Florida, Southeast, Gulf Coast) - Overheating is more common. Owners in these regions often remove fly sheets when the heat index climbs, or choose the lightest possible mesh materials.

The bottom line: your local climate should inform your fly sheet decisions more than any generic temperature guideline.

Regional humidity levels significantly impact how horses regulate heat, requiring different fly sheet strategies for dry versus humid environments.

When to remove the fly sheet

There are clear situations when the fly sheet should come off regardless of your usual routine:

Heat index over 90°F without adequate shade or breeze - The combination of high heat and humidity creates risk
Your horse is showing signs of overheating - Trust what you observe over any temperature guideline
Peak sun hours with no shade access - 10am to 4pm is when solar radiation is most intense
Nighttime if temperatures drop significantly - Many horses don't need sheets overnight when flies are less active

Some owners in hot climates switch to night turnout during summer months. The temperatures are cooler, flies are less active, and horses can get their grazing time without the heat stress.

Protect your horse with breathable fly protection

Fly sheets and hot weather aren't mutually exclusive. With the right material, proper fit, and attention to environmental factors, your horse can stay protected from insects without overheating.

The key is understanding that there's no magic temperature number. A fly sheet in 95°F dry heat with shade and breeze can be safer than no fly sheet in 80°F humid conditions with direct sun exposure.

At Kensington, we believe in "products that protect & perform." Our Textilene® fabric technology has been trusted since 1954 because it strikes the right balance: serious protection that doesn't compromise breathability. We operate under a simple principle: if you need sunglasses, your horse needs them too.

Ready to find the right fly protection for your climate? Explore our complete fly protection collection, including our fly mask guide for complete coverage from ears to tail.

Frequently Asked Questions

Can I leave a fly sheet on my horse in 100 degree weather?

It depends on humidity and shade. In dry climates with access to shade and breeze, many horses do fine in fly sheets at 100°F+. In humid conditions, this temperature is generally too hot for any fly sheet. Monitor your horse for signs of overheating regardless of the temperature.

What is the best fly sheet material for hot weather?

Ripstop Nylon Mesh and lightweight mosquito mesh materials offer the best airflow for hot weather. Textilene®, while stiffer, creates natural air channels by standing away from the horse's body. Avoid heavy vinyl-coated materials in extreme heat.

Do fly sheets actually keep horses cooler?

Light-colored or white fly sheets can reflect UV rays and keep dark horses cooler than no sheet at all. However, heavy or poorly ventilated fly sheets can trap heat. The cooling effect depends on material, color, and fit.

Should I remove my horse's fly sheet at night?

Many owners remove fly sheets at night when temperatures drop and flies are less active. However, if your horse has sweet itch or severe fly allergies, overnight protection may still be necessary. Consider night turnout when daytime heat is extreme.

How do I know if my horse is too hot under a fly sheet?

Check for excessive sweating under the sheet, rapid breathing (over 16 breaths per minute), lethargy, or skin that feels hot to the touch. If you observe these signs, remove the sheet immediately and provide shade and water.