Wind gust

The difference between wind gusts and sustained wind speeds

While related, a wind gust is distinctly different from what meteorologists refer to as sustained wind speed. Sustained wind speed is the average speed of the wind over a longer period—typically between two and ten minutes. This average provides a general indication of the wind's ongoing force.

In contrast, a wind gust represents a sharp, fleeting peak in wind speed. Imagine sustained wind as a steady flow of water in a river; a gust would be like a sudden surge of water rushing past. This brief spike can be significantly stronger than the sustained wind, making gusts particularly hazardous despite their short duration. For example, a forecast might report a sustained wind of 20 km/h with gusts up to 40 km/h, meaning the wind will generally blow at 20 km/h but will occasionally spike to 40 km/h for very short periods.

How wind gusts are measured

Measuring wind gusts requires instruments that can rapidly detect changes in wind speed. The primary tool is an anemometer—typically a cup or sonic anemometer.

These devices continuously record wind speed and can detect the highest instantaneous speed over a short time frame, usually 3 to 5 seconds, or even a single second for peak gust detection. This rapid sampling ensures that brief surges in wind are captured, providing critical data that sustained wind measurements alone cannot.

What causes gusts of wind?

Wind gusts are primarily caused by turbulent airflow in the atmosphere, which arises from several factors:

Atmospheric instability

‍When the atmosphere is unstable, warm air rises and cooler air sinks, creating vertical air currents. These currents can pull faster-moving air from higher altitudes down to the surface, causing sudden increases in wind speed.

Surface friction and obstructions

‍As wind moves across the ground, it encounters friction from terrain and obstacles such as buildings, trees, and hills. This interaction creates eddies and swirling pockets of air. When these reach a certain point, they can cause a momentary increase in wind speed—a gust. It’s similar to how water flows around rocks in a stream, becoming choppy and uneven.

Convective activity

‍Storms, especially thunderstorms, are a major source of strong gusts. Intense updrafts and downdrafts within a storm can send cold, dense air rushing downward. When this air hits the ground, it spreads out quickly, creating powerful gust fronts or straight-line winds.

In short, gusts are a natural result of the atmosphere’s chaotic and dynamic behavior, influenced by temperature differences, terrain, and weather systems.

What is a strong wind gust?

What qualifies as a “strong” gust depends on the context, but typically refers to wind speeds capable of causing noticeable impact or damage. Local thresholds vary, but common benchmarks include:

Moderate gusts (40–60 km/h):

‍ – Difficult walking conditions
– Leaves rustling, small branches may break
– High-sided vehicles affected

Strong gusts (60–80 km/h):

‍ – Hard to stand upright
– Movement of unsecured objects
– Larger tree branches may snap
– Minor structural damage possible

‍Damaging gusts (above 80 km/h):

‍ – Risk of power outages and falling trees
– Widespread property damage
– Dangerous driving conditions
– Associated with tropical storm force winds (starting around 63 km/h)

Local weather advisories define “strong wind warnings” using thresholds relevant to the region’s typical conditions and hazards.

How wind gusts are included in weather forecasts

Wind gusts are typically included in detailed weather forecasts, especially when they are expected to exceed sustained wind speeds or pose safety risks. Providing this information is critical, as gusts—though brief—can cause more damage than the average wind speed.

Forecasters usually report both sustained wind speed and maximum expected gusts, for example:  “Winds 15 to 25 km/h, gusting to 40 km/h.” This helps individuals and industries prepare for sudden wind surges. Construction crews, pilots, sailors, and outdoor planners all benefit from knowing when to expect potentially hazardous bursts of wind.

In severe weather conditions, such as thunderstorms or strong frontal systems, gusts are often the most important wind-related factor to communicate due to their damage potential.