How your weather forecast can help protect you from ticks

Most of us check the weather forecast to decide what to wear, or to see if we need to carry an umbrella. But as tick bites and Lyme disease surge across the country, that forecast could be your first line of defense against these blood-seeking parasites.

Emergency room visits due to tick bites hit a 10-year high in the U.S. this spring, according to the Centers for Disease Control and Prevention. The record surge was seen in all regions except the South Central U.S., the agency reported.

Those living in the Northeast are all too familiar with the surge in tick activity during the spring and summer, but you may be surprised that a refreshing summer rain show doesn’t wash away the danger — it amplifies it.

(MORE: Ticks 101 - everything you need to know)

Unlike humans, ticks can’t drink water. Instead, they absorb it directly from the air through their outer shell. This biological quirk makes them especially sensitive to humidity levels, so your weather app could hold the key to predicting when they’ll be outside in huge numbers.

Research published in the Journal of Medical Entomology reveals the magic number: 82% relative humidity. Above this threshold, blacklegged ticks (one of the primary carriers of Lyme disease) become active hunters, questing or hunting for hosts. Below the threshold for eight hours or more, their activity plummets, and they begin to die from dehydration.

Why rain creates the perfect storm

During rainfall, tick activity drops as they retreat into leaf litter for protection. But once the rain stops, humidity levels spike — often well above that critical 82% mark.

This post-rain window creates ideal hunting conditions, with ticks emerging to quest longer and climb higher on grass and other vegetation than during dry periods.

The effect can last for days. Leaf litter — where ticks spend most of their time — naturally holds higher humidity levels, creating a refuge that prolongs their active hunting period well beyond what airport weather stations might suggest.

Temperature adds another layer

Humidity isn't the only weather factor at play. Researchers found that tick activity switches on around 45 degrees, peaks near 77 degrees, and shuts down by 86 degrees as hot, dry air drives them deeper into vegetation.

So blazing hot, dry days actually make it harder for ticks to survive and hunt. The real danger zone? Mild and humid conditions — exactly what you get in the hours and days following summer rain showers.

(MORE: Lyme disease isn’t the only threat from ticks)

Reading your forecast like a tick expert

So before you head out on that hike, or mow the lawn or do some gardening in your backyard, here’s what to look for to give you a heads up for potential tick activity.

Higher risk days:

• "Scattered showers" followed by "partly cloudy and humid"
• Post-rain humidity above 80%
• Mild temperatures (70-80°F) with high humidity
• Overcast, muggy conditions

Lower risk days:

• Hot, dry conditions above 86°F
• Extended dry spells with low humidity
• Bright, sunny days with low moisture

So armed with all that information that you can easily track with The Weather Channel app (You can download it in the Apple store or on Google Play), you can delay outdoor activities or maybe stick to the center of trails and avoid brushing up against vegetation.

Of course, no matter the weather, you should be protecting yourself by spraying your clothes with EPA-approved repellents, and wearing long sleeves or long pants to keep ticks away from your skin.

You also want to do a thorough tick check immediately after an outdoor adventure. We have this great how-to video on tick detection and removal.

(MORE: Tick safety for pets)