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What Causes Hail in the Summer? Understanding the Science, Risks, and Impacts

Delve into the science behind summer hailstorms, their formation, impacts on nature and agriculture, and essential safety tips.

By Sneha Tete, Integrated MA, Certified Relationship Coach

Created on Sep 27, 2025

Delve into the science behind summer hailstorms, their formation, impacts on nature and agriculture, and essential safety tips.

Hailstorms can take many by surprise, especially when they strike during the heat of summer. Although often associated with thunderstorms, the science behind summer hailstorms is complex and fascinating. This article explores how hail forms, why it’s common in warm seasons, its effects on humans and the environment, and what you can do to protect yourself and your property from this powerful force of nature.

What Is Hail?

Hail is a type of precipitation that forms as balls or irregular lumps of ice, called hailstones, which fall from thunderstorm clouds. Unlike sleet or snow, hail is made of solid, layered ice and can range in size from tiny pellets to larger than golf balls. Large hailstones can cause extensive damage to crops, vehicles, roofs, and even injure animals or people in their path.

How Does Hail Form?

Hail develops inside strong thunderstorm clouds, especially those containing intense updrafts, abundant moisture, and significant temperature differences between upper and lower parts of the cloud. The process can be broken down as follows:

Formation of Embryos: Tiny ice pellets (embryos) form when supercooled water droplets in the cloud freeze upon contact with dust particles or other ice.
Growth in Updraft: Strong updrafts within the storm cloud carry these ice embryos upward, sometimes several times, through layers of the cloud. In each ascent, they encounter more supercooled water, which freezes onto their surface and causes the hailstone to grow larger.
Layering Effect: Each circuit through the cloud adds new layers of ice, producing the distinctive concentric rings sometimes seen when hailstones are cut open.
Descent to the Ground: When the hailstone becomes too heavy for the updraft to support, it falls to the ground as hail. The layered nature of hailstones often reveals the number of times they cycled through the cloud.

Hailstones may remain in the updraft for several minutes, growing larger with each cycle before gravity prevails.

Why Is Hail More Common in Summer?

It may seem unusual for ice to fall from the sky during the warmest months, but hail is actually most frequent in the spring and summer. The key reason lies in the characteristics of summer thunderstorms:

Atmospheric Instability: Warm surface temperatures heat the air, causing it to rise and form powerful updrafts within thunderclouds, which are crucial for hailstone growth.
High Moisture Content: Moist summer air fuels large, energetic thunderstorm systems capable of supporting hail formation.
Strong Wind Shear: Differences in wind speed and direction with altitude (wind shear) can help storms organize and persist, creating ideal hail-producing conditions.

Thus, the collision of warm, moist air at the earth’s surface and cold air aloft—a hallmark of summer and spring weather—creates the unstable atmospheric environments most conducive to hailstorms.

The Anatomy of a Hailstorm

A typical hailstorm evolves within a powerful (often severe), vertically developed thunderstorm cloud known as a cumulonimbus. The development process includes:

Updraft Region: Carries warm, moist air high into the cloud, cooling it rapidly.
Supercooled Water Drops: Occur in the upper cloud layers, remaining liquid below freezing point due to lack of nuclei to freeze upon.
Hail Growth Zone: Here, ice embryos are repeatedly carried through supercooled droplets, adding successive layers of ice.
Heavy Hail Core: Areas of greatest updraft often correspond to the core of the storm where the largest hailstones form and eventually fall.

Table: Key Ingredients for Hail Formation

Ingredient	Role in Hail Formation
Intense Updraft	Suspends hailstones high in cloud for longer, allowing them to grow
Supercooled Water	Freeze onto hailstone’s surface, increasing size
Temperature Gradient	Provides right conditions for transitioning water to ice
Moisture-Laden Air	Fuels cloud growth and sustains storm structure
Wind Shear	Organizes storm, prolonging updrafts and severity

How Big Can Hailstones Get?

Hailstones vary in size and shape. They can be as small as peas or as large as baseballs—or rarely, even bigger. The National Weather Service classifies hail by diameter:

Pea: ~0.25 inches (6 mm)
Marble: ~0.5 inches (13 mm)
Quarter: ~1 inch (25 mm)
Golf ball: ~1.75 inches (44 mm)
Baseball: ~2.75 inches (70 mm)
Softball: ~4.5 inches (114 mm)

Very large hail can reach speeds over 100 mph (160 kph) as it falls, and even small stones can inflict injury or damage property.

Why Does Hail Fall as Ice During Hot Weather?

Despite occurring in warm weather, hailstones survive their descent because they originate in very cold regions of the storm—often near or below -40°F/C at high altitudes. The following factors help hailstones stay frozen on the way down:

Fast Descent: Large hailstones fall quickly, limiting their time exposed to warmer, lower air layers.
Ice Melting Resistance: The large mass and layered structure allow them to remain frozen longer.
Hail Core Fall: Sometimes hail falls in such volume that air near the surface is briefly cooled by melting hail, further preserving the ice.

Environmental and Societal Impacts of Hailstorms

Hailstorms are notorious for causing sudden and extensive damage, especially in areas where they are frequent. Impacts can include:

Agricultural Damage: One of the most destructive effects of hail is to crops, particularly delicate fruits and vegetables. A single storm can destroy entire harvests, resulting in significant economic losses for farmers.
Tree and Plant Damage: Hail can strip trees of leaves, break branches, and injure plants. Healthy trees often recover, but severe storms can make them more vulnerable to disease and pests.
Property Damage: Cars, roofs, windows, and outdoor structures are all at risk, with roofing materials and skylights especially susceptible to breakage from larger hailstones.
Personal Injury: Large, fast-falling hail can cause bruises, cuts, or more serious injuries to humans and animals caught outdoors.
Infrastructure and Utility Damage: Hailstorms may damage power lines, cause flooding from blocked gutters, or even disrupt communication networks.

Some of the most severe hailstorms have left behind fields blanketed with ice, shredded plants and gardens, and battered buildings and vehicles.

How to Protect Yourself and Your Property During Hailstorms

While forecasting hail remains challenging, some steps can reduce risks to life and property:

Stay Indoors: Seek shelter in a sturdy building. Avoid windows and glass doors where possible.
Protect Vehicles: Move cars into a garage, carport, or under sturdy shelter if there is advance warning.
Secure Outdoor Items: Bring patio furniture, grills, and other objects indoors to prevent damage.
Use Storm-Resistant Materials: Consider impact-resistant roofing and skylights in hail-prone areas.
Agricultural Protection: Farmers can employ hail netting over vulnerable crops or plant in dispersed locations to reduce risk of total loss.
Have Emergency Kits Ready: Keep first aid supplies accessible in case of injury and be prepared for power outages that may follow a severe storm.

Frequently Asked Questions (FAQs)

Q: Can hailstorms be predicted?

A: Meteorologists use advanced radar and satellite technology to forecast severe thunderstorms that might produce hail, but predicting the exact location, timing, and size of hail remains difficult due to the localised and complex dynamics involved in storm formation.

Q: Are hailstorms getting worse with climate change?

A: Some studies suggest that shifts in atmospheric patterns due to climate change could affect the frequency and severity of hailstorms. However, regional differences and complex weather factors mean more research is needed for definitive answers.

Q: What is the largest recorded hailstone?

A: The largest officially recorded hailstone in the U.S. fell in Vivian, South Dakota, in 2010. It measured eight inches (about 20 cm) in diameter and weighed nearly two pounds (0.88 kg).

Q: Do hailstones always have concentric layers?

A: Most hailstones show visible layering, which reflects their repeated journeys through different parts of the storm cloud before falling, but not all hailstones are perfectly concentric due to variable storm conditions.

Q: Why is hail more common in some regions?

A: Areas with frequent, powerful thunderstorms and strong updrafts are more prone to hail. In North America, for example, the central Plains (“Hail Alley”) experience more severe hail due to ideal storm conditions.

Key Takeaways

Hail forms in thunderstorm clouds with strong updrafts, supercooled water, and significant temperature gradients.
It is most common in spring and summer due to the atmospheric instability and energy present at these times.
Hail can cause substantial damage to crops, trees, property, and people.
Preparation and prompt response are key to minimizing the risks and impacts associated with hailstorms.