Key Difference: Mostly Sunny is when the average sky is covered 1/8 to 2/8 with opaque clouds. Partly Cloudy is when the average sky is covered 3/8 to 4/8 with opaque clouds.

The weather is a very important aspect of a person’s day and it can also affect the mood of the person in various ways. Today weather can be viewed in many ways, on the TV, on the radio, maybe an app, the internet, etc. Weather can also be used to determine the temperature, the conditions, humidity, cloud cover, etc.

Partly cloudy and mostly sunny are two words that are often heard along with a string of other words such as sunny, partly sunny, mostly cloudy and cloudy, that are used to describe the sky conditions. Though it may seem that partly cloudy and mostly sunny mean the same thing, these are in fact different from each other. The main difference lies in the cloud cover and the amount of precipitation during both of these conditions.

‘Partly cloudy’ refers to when there is more clouds compared to sun, while ‘mostly sunny’ is when there is more sun and less clouds. ABC 5 states the difference as during partly cloudy there is 30-70% cloud coverage in the sky, which is the same as ‘Partly Sunny’, while cloud coverage ranges from 10-30% during mostly sunny. Mostly sunny is also a term that is often heard during the day time, while partly cloudy can be used during day and night, but generally leans towards night time.

The National Weather Service defines both these terms as:

• Mostly Sunny: When the predominant/average sky condition is covered 1/8 to 2/8 with opaque (not transparent) clouds. Same as Mostly Clear.

• Partly Cloudy: When the predominant/average sky condition is covered 3/8 to 4/8 with opaque (not transparent) clouds. Same as Partly Sunny.

Image Courtesy: weather.thewest.yahoo.com.au, iconarchive.com