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Why Do Flies Bite Before Is Starts Raining?

Serving Charlotte | Raleigh - Durham | Greensboro

Have you heard someone say, “The flies are biting, so rain is coming”? There might be some truth to this old saying. As part of our “You Ask, We Verify” series, we’re exploring whether there are any links between increased fly activity and certain weather conditions.

We examine some possible causes of this phenomenon, shed light on fly behavior, and offer tips on managing these pesky insects.

Are Flies More Aggressive When It’s About to Rain?

Carol from Greensboro asked our VERIFY team if there was any truth to the idea that when flies bite, it’s going to rain. She observed an increase in fly bites while volunteering at a local playground and wondered if it was a sign of impending rain.

To help answer this question, we consulted Frank Fowler, a biologist and former vice president of McNeely Pest Control, Inc. (now part of the Bug Out Brand), to find out.

Why Do Flies Bite?

Frank Fowler confirmed that he had always heard what Carol heard — biting flies mean pending rain. Initially, he thought it was an old wives’ tale until he studied insects. He explained that many animals can detect changes in the weather before they occur and respond by taking shelter. The lower barometric pressure preceding a storm can cause animals to want to feed more aggressively. Thus, flies sometimes bite humans to get blood.

Older generations, who spent more time outside than working adults today, noticed this behavior and linked it to incoming rain.

Types of Biting Flies

There are several types of flies known to bite, including:

  • Horse Flies: Large, aggressive flies known for their painful bites.
  • Deer Flies: Smaller than horse flies but still quite aggressive.
  • Stable Flies: Often mistaken for house flies, these pests bite humans and animals.

These flies seek out blood meals for nourishment, especially when the weather changes, leading to increased biting activity.

Managing Fly Bites

If you’re experiencing more fly bites, consider wearing protective clothing such as long sleeves and pants to protect your skin, applying insect repellent to exposed areas to deter flies, and staying indoors during peak biting times, especially when rain is forecasted.

Effective Fly Control Methods

To manage fly populations around your environment, eliminate breeding sites by removing standing water and decaying organic matter where flies lay eggs. Additionally, using various fly traps can help reduce their numbers. Maintaining cleanliness through regular cleaning and proper waste management can also deter flies from settling.

Final Tips for Fly Control

When flies start biting, they may be trying to tell you something. Check your local weather forecast — as rain may be on the way. If you need help with a fly infestation, consider contacting our fly control experts, who can provide long-term prevention strategies and solutions.

For more detailed information about the most common types of flies found in North Carolina, visit our species pages. Understanding why flies bite and how to manage them can help you stay comfortable, even when the weather changes.

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