Do Thermals Rise on Cloudy Days?

On cloudy days, a question often arises about the presence of thermals. Contrary to popular belief, thermals do indeed rise on overcast days. While it’s true that the efficiency of thermal development is reduced due to the obstructed sunlight, there are instances where the instability of the atmosphere compensates for this. Although the amount of UV radiation that reaches the Earth's surface is diminished, it still manages to heat the ground to some extent. This residual heating is occasionally sufficient to generate thermals, albeit not as effectively as on clear, sunny days. Consequently, while overcast conditions are generally not as favorable for thermal activities, there are instances where they can surprise with their strength and potency. It’s this intriguing interplay of atmospheric instability and residual heating that allows thermals to persist on cloudy days, offering a captivating phenomenon worthy of exploration and understanding.

Do Thermals Go Uphill in the Morning?

Thermals, the rising columns of warm air, do indeed tend to go uphill in the morning. This phenomenon occurs due to the basic principle that warmer air is less dense than cool air. As the sun begins to heat up the hillside, the surrounding air on the hillside warms up as well. This warm air becomes less dense than the cooler air surrounding it, and as a result, it starts to rise.

Conversely, in the evening when the sun goes down, the hillside begins to cool down, and the hot air pockets that were keeping the thermals aloft start to dissipate. As the warm air cools and becomes denser, it can no longer overcome the downward pull of gravity. Consequently, the thermals start to fall, and the once upward motion transforms into a downward motion causing them to descend.

It’s important to note that while thermals generally follow this pattern, there can be exceptions depending on various factors such as weather conditions, wind patterns, and topography. Cloudy days, for instance, can impact thermal movement. The presence of clouds can limit the amount of sunlight reaching the hillside, thereby reducing the heat and the formation of strong thermals. However, thermals can still form to some extent on cloudy days, but they might not be as strong or as consistent as during clear, sunny conditions.

How Weather Conditions Can Affect Thermal Formation and Movement

Weather conditions play a crucial role in the formation and movement of thermals, even on cloudy days. Thermals are pockets of warm air that rise due to their lower density compared to the surrounding cooler air. On sunny days, the ground heats up, causing the air above it to warm and form thermals. However, on cloudy days, this process isn’t as pronounced.

Cloud cover acts as a barrier, limiting the amount of sunlight that reaches the surface. Consequently, the ground doesn’t warm up as much, resulting in weaker thermals. Clouds can also trap heat near the surface, preventing it from rising and creating strong upward currents. As a result, the vertical movement of thermals may be less pronounced on cloudy days.

Moreover, clouds can influence the stability of the atmosphere. Different types of clouds, such as cumulus and stratocumulus, can indicate specific atmospheric conditions. These conditions may affect the strength and behavior of thermals. For example, cumulus clouds with well-defined vertical development can enhance thermal activity, while stratocumulus clouds, which are more horizontally spread, may suppress thermal formation.

In summary, while thermals can still form and rise on cloudy days, their strength and vertical movement are typically weaker compared to sunny days. The presence of clouds influences the heating of the ground and stability of the atmosphere, impacting the formation and behavior of thermals.

In addition to reducing visibility and clarity, rain and fog can significantly impact the effectiveness of thermal imaging systems. The presence of water droplets in the atmosphere causes light to scatter, inhibiting the infrared signal transmitted by thermal cameras. The higher the concentration of droplets, the more pronounced the decrease in infrared signal. As a result, thermals are heavily influenced by rain and fog, affecting their range and diminishing their overall capabilities.

How Does Rain Affect Thermals?

When it comes to discussing the impact of rain on thermals, it’s important to consider the limitations imposed on thermal imaging systems due to the presence of moisture. Fog and rain can have a significant effect on the range and effectiveness of thermal imaging technology, primarily because they cause the scattering of light off water droplets. As these droplets become denser in a rainy or foggy environment, they can greatly diminish the infrared signal that’s essential for thermal imaging.

The scattering of light off water droplets in the atmosphere can severely limit the range of a thermal imaging system. This means that the thermal cameras ability to detect and capture thermal signatures from objects in the distance becomes compromised.

Moreover, the presence of rain or fog also tends to decrease the overall clarity and sharpness of thermal images. The scattered light can create a hazy effect, making it more challenging to distinguish details and accurately interpret the thermal signatures of objects. This can pose significant challenges in various applications such as surveillance, search and rescue operations, and industrial inspections, where clear thermal imaging is crucial.

In addition to limited range and reduced image quality, rain also affects thermals by impacting their behavior. In a rainy environment, the moist air and water-cooled surfaces can alter the temperature differentials that create thermals in the first place. The cooling effect of rain can disrupt the convection currents responsible for the formation and movement of thermals, potentially diminishing their strength and duration.

How Rain Affects the Performance of Thermal Imaging Drones and Unmanned Aerial Vehicles (UAVs)

  • Increased difficulty in detecting objects
  • Reduced range and accuracy
  • Impaired image quality
  • Potential damage to equipment
  • Limited flight time due to weather conditions
  • Reduced overall efficiency and effectiveness


The presence of clouds doesn’t completely hinder the development of thermals, as there are various factors at play. In certain cases, the instability of the atmosphere can actually facilitate the formation of thermals, allowing them to rise despite the cloudy conditions. Although the efficiency may be reduced due to the obstructed UV radiation, it’s important to remember that thermals can still be strong and influential even on overcast days. Therefore, it’s crucial for pilots, meteorologists, and aviation enthusiasts to not discount the potential of thermals on cloudy days and to consider the intricate dynamics of the atmosphere for accurate assessments and predictions.

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