In autumn, it's not uncommon to find fields and gardens covered with a fine layer of water droplets in the morning: this is dew. But why does dew seem more frequent during this time of year?
Dew forms when the moisture present in the air condenses into small droplets on cold surfaces, such as leaves, grass, or cars. This phenomenon generally occurs during the night or early morning when the air temperature decreases.
Illustrative image Pixabay
In autumn, nights become cooler and longer, which promotes the formation of dew.
Here's how it works: the temperature drops during the night, and if it falls low enough, surfaces on the ground (such as plants or the ground itself) cool down faster than the air around them. The air always contains a certain amount of moisture in the form of water vapor. When the air near these cold surfaces cools even further, it can reach a point where it can no longer hold as much moisture. This point is called the "dew point." Once the air temperature drops below that point, the moisture condenses into droplets: this is dew.
In autumn, temperature differences between day and night are more pronounced than in summer. Days can still be fairly warm, but the nights are significantly cooler. This drop in nighttime temperature often reaches the dew point, which explains why dew is more frequent during this time of year.
Additionally, autumn air often contains more humidity than the dry air of the summer months, due to the rains and the general cooling of the atmosphere. This excess moisture, combined with cooler nights, creates ideal conditions for dew formation.
Dew is thus more frequent in autumn because the nights are longer and cooler, and the air is often more humid. This phenomenon is an illustration of how temperature and humidity interact in nature, forming these characteristic water droplets on autumn mornings.