What Are Clear Skies?
Clear skies are a weather condition in which little or no cloud cover is present. During the day, this generally means an unobstructed view of the blue sky, while at night it provides a clearer view of the Moon, stars and other objects in the night sky.
Clear conditions are commonly associated with fair weather, but they do not necessarily mean temperatures will be warm. Clear skies can occur during hot summer weather as well as extremely cold winter conditions.
The lack of clouds also affects how quickly the surface heats and cools. More sunlight can reach the ground during the day, while heat can escape more readily from the surface on a clear night.
Related Conditions
| Condition | Description |
|---|---|
| Partly Cloudy | A sky condition where some clouds are present but a substantial portion of the sky remains clear. |
| Mostly Clear | A sky condition with only a small amount of cloud cover and predominantly clear skies. |
| Cloudless Sky | A sky with essentially no visible cloud cover. |
| Fair Weather | Generally calm or settled weather with limited cloud cover and little or no precipitation. |
| High Pressure | An atmospheric pattern commonly associated with sinking air, settled weather and periods of clear sky. |
Related Alerts
| Alert | Description |
|---|---|
| Frost Advisory | Issued when temperatures near the ground are expected to become cold enough for frost to develop during the growing season. |
| Extreme Cold Warning | Warns when very low temperatures or wind chill create dangerous cold conditions. |
| Heat Warning | Warns when temperatures or humidex values are expected to create potentially dangerous heat conditions. |
| Air Quality Warning | Warns when poor air quality is expected to pose an increased health risk. |
| Yellow Warning – Air Quality | Indicates potentially hazardous air-quality conditions that may affect sensitive individuals. |
What Causes Clear Skies?
Clear skies generally develop when the atmosphere does not contain enough rising, cooling and condensing moisture to produce widespread clouds.
High-pressure systems commonly create these conditions. Air within an area of high pressure tends to sink. As the air descends, it warms and becomes less favourable for condensation and cloud formation.
Dry air can also contribute to clear skies. When the atmosphere contains relatively little moisture, clouds are less likely to develop even when other weather conditions change.
Clear skies can persist when a high-pressure system remains over a region for several days. However, clouds may quickly return as moisture increases or an approaching weather system causes air to rise.
Clear conditions can also have a noticeable effect on temperature. During the day, direct sunlight can warm the surface. At night, the absence of clouds allows heat to escape more efficiently, sometimes producing a significant temperature drop.
This nighttime cooling can be particularly important during spring and fall. Clear, calm nights can allow temperatures near the ground to fall enough for frost to develop, which is why clear skies can sometimes accompany conditions that lead to a Frost Advisory.
FAQ
Clear skies generally mean little or no cloud cover is expected during the forecast period.
Not necessarily. A sky can still be described as clear when a very small amount of cloud is present.
Clear conditions have little or no cloud cover, while partly cloudy conditions have a more noticeable mixture of clouds and open sky.
High pressure commonly produces sinking air. As that air descends and warms, condensation and widespread cloud formation become less likely.