For paragliders, hang gliders, and other soaring enthusiasts, finding the best thermals is the key to achieving long, sustained flights. Thermals, rising columns of warm air, provide the lift needed to keep gliders aloft and enable pilots to gain altitude for cross‑country flights or extended soaring sessions. While thermals can be found year‑round, the conditions that create them vary depending on the season, time of day, and geographical location. Understanding the nuances of thermal activity throughout the year is crucial for pilots who want to maximize their flying experience and safety.
In this article, we will explore how thermals form, the best times to find them in each season, and how to identify the optimal conditions for thermal flying. Whether you are a seasoned pilot or a beginner, this guide will provide you with the knowledge needed to make the most of thermal conditions throughout the year.
Understanding Thermals
Before delving into the seasonal aspects of thermal flying, it's important to understand what thermals are and how they work. A thermal is simply a rising column of air caused by uneven heating of the Earth's surface. The sun warms the ground, and when the air near the surface heats up, it becomes less dense than the cooler air above it, causing it to rise. As the warm air rises, it creates a thermal updraft that can lift a paraglider or hang glider.
Key factors influencing thermal development include:
- Solar heating : The sun's energy heats the Earth's surface, and this heating is stronger on darker surfaces like rocks, roads, or fields.
- Wind : Wind direction and speed can influence the formation of thermals, as wind can push rising air or break up thermal columns.
- Topography : Mountains, valleys, and ridgelines can help create or concentrate thermals, making these areas particularly favorable for soaring.
Thermals are generally most active in the afternoon when the sun has had the most time to heat the ground. However, other factors such as time of day, geography, and weather systems can all impact thermal conditions.
Thermal Flying Throughout the Seasons
While thermals can be found at any time of the year, each season brings its own unique challenges and opportunities. Let's explore what to expect in each season and how to find the best thermals.
1. Spring: The Awakening of Thermals
Spring is a transitional season where pilots can experience some of the best thermals of the year. As the days grow longer and temperatures warm up, the sun begins to heat the ground more effectively. The difference in temperature between the ground and the upper atmosphere is typically large, leading to strong thermal activity.
Key characteristics of spring thermals:
- Warm afternoons : By midday, the sun has warmed the ground sufficiently to generate strong thermals, often beginning around noon and continuing until late afternoon.
- Inconsistent thermal strength : Spring thermals may vary in strength depending on how quickly the weather warms up. It's important to monitor the local conditions to gauge thermal activity.
- Good for beginners : Since the air tends to be smoother, spring thermals can be more predictable and manageable for less experienced pilots.
In spring, it's best to head out early in the day or during the warmest part of the afternoon, when the sun is most effective at creating thermals. Look for areas with good sunlight exposure, such as open fields, south‑facing slopes, or rocky outcrops.
2. Summer: The Peak of Thermal Activity
Summer is the most consistent and productive season for thermal flying. The longer days and intense solar heating create some of the strongest thermals of the year. This is the ideal season for cross‑country flights and extended soaring.
Key characteristics of summer thermals:
- Strong thermals : Summer heat can create very strong thermals, which can carry pilots to high altitudes. In some regions, thermals can be powerful enough to create turbulence, making it a more challenging environment for beginners.
- Early morning starts : During the hottest days, thermals often start forming early in the morning, well before noon. However, they peak during the afternoon when the sun has had time to heat the ground.
- Turbulent conditions : Strong thermals can lead to turbulent air, especially at higher altitudes. While experienced pilots can use this to their advantage, beginners should be cautious and stay within their comfort zone.
In summer, look for large open areas with no obstructions, as thermals are most likely to form over sun‑drenched ground. Areas with minimal wind are also ideal, as thermals will be easier to spot and navigate.
3. Autumn: Transition to Cooler Conditions
As summer gives way to autumn, the sun's strength begins to wane, and the thermal conditions start to change. While autumn still offers good thermal conditions, they are generally less intense and less consistent than in summer. The weather becomes cooler, and the ground heats up more slowly, resulting in weaker thermals.
Key characteristics of autumn thermals:
- Lower thermal strength : Thermals may be weaker and less predictable as the ground cools off faster. However, they can still provide decent lift, especially during the warmest days of the season.
- Less consistent : Autumn weather can be unpredictable, with some days experiencing good thermal activity and others offering very little lift. Pilots should be prepared for varied conditions.
- Excellent for local flights : Due to the less intense thermals, autumn is a great time for local soaring and short cross‑country flights, especially if you enjoy scenic views and calmer weather.
To maximize your autumn flights, aim to fly on days when there is significant sun and light winds. Look for spots with good sun exposure, especially south‑facing slopes or open fields.
4. Winter: The Quiet Season
Winter presents the most challenging conditions for thermal flying. In many areas, thermals are much weaker or nonexistent, and cold air can make it difficult for thermals to form. However, in regions with relatively mild winters or strong sunlight, it's still possible to catch a few thermals and enjoy a brief flight.
Key characteristics of winter thermals:
- Cold, weak thermals : Cold air and shorter days make thermals less likely to form. Even if thermals do occur, they tend to be weaker and less reliable.
- Best in sunny locations : In regions where the sun is strong enough to heat the ground, thermals may still form, but they will likely be weak and short‑lived.
- Limited flying time : Because of the cold temperatures and weak thermals, winter flying is often limited to short flights close to the launch site.
Winter is not typically the season for long‑distance flying or ambitious cross‑country flights. If you're determined to fly, it's best to focus on shorter, local flights and monitor the weather carefully. Opt for regions where sunshine and light winds can still generate thermals.
How to Find the Best Thermals Year‑Round
Finding thermals year‑round requires not just understanding seasonal variations, but also being able to read the signs that indicate thermal activity. Here are a few tips to help you identify thermals, no matter the season:
1. Look for Heat Sources
Thermals are often created by the sun's heat, so seek out areas where the ground is heated most effectively. These areas include:
- Open fields : Areas of land that are exposed to direct sunlight.
- Rocky terrain : Rocks and cliffs absorb more heat than grass or soil, making them good sources of thermals.
- South‑facing slopes : In the Northern Hemisphere, south‑facing slopes receive more sunlight, making them ideal for thermal formation.
2. Observe the Clouds
Clouds are often a good indicator of thermal activity. Cumulus clouds form when warm, rising air reaches the cooler levels of the atmosphere and condenses. If you see cumulus clouds developing, it often means thermals are strong in the area. Conversely, if there are no clouds, thermals may be weak or nonexistent.
3. Check the Winds
Light winds are generally better for thermals because they allow the warm air to rise without being pushed sideways. However, winds can also concentrate thermals along ridgelines or in valleys, which can create more consistent lifting conditions. On windy days, look for areas where the wind may have created a convergence zone, where thermals are more likely to form.
Conclusion
Finding the best thermals all year round is a skill that requires an understanding of both seasonal patterns and local conditions. While summer provides the most consistent and intense thermals, each season offers unique opportunities for soaring. By learning how thermals behave during different times of the year and reading the subtle signs in the environment, pilots can enjoy flying year‑round, regardless of the weather or season. Understanding these seasonal secrets will allow you to maximize your soaring experience and fly safely, no matter the conditions.