This report describes the typical weather at the Kirkwall Airport (Kirkwall, United Kingdom) weather station over the course of an average May. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Kirkwall has a mild humid temperate climate with warm summers and no dry season. The area within 25 mi of this station is covered by oceans and seas (82%) and grasslands (16%).
The month of May is characterized by gradually rising daily high temperatures, with daily highs increasing from 50°F to 55°F over the course of the month, exceeding 60°F or dropping below 45°F only one day in ten.
Over the course of May, the length of the day is very rapidly increasing. From the start to the end of the month, the length of the day increases by 2:05 hours, implying an average day-over-day increase of 4.0 minutes.
The shortest day of the month is May 1 with 15:52 hours of daylight; the longest day is May 31 with 17:57 hours of daylight.
The earliest sunrise is at 4:12am on May 30; the latest sunset is at 10:09pm on May 31; the latest sunrise is at 5:13am on May 1; the earliest sunset is at 9:05pm on May 1.
Daylight saving time is observed in 2012 but it neither starts nor ends in May, so the entire month is in daylight time.
The median cloud cover is 83% (mostly cloudy) and does not vary substantially over the course of the month.
On May 16, a representative day, the sky is clear or mostly clear 20% of the time, partly cloudy 24% of the time, and mostly cloudy or overcast 48% of the time.
The average probability that some form of precipitation will be observed in a given day is 74%, with little variation over the course of the month.
Throughout May, the most common forms of precipitation are moderate rain and light rain.
Moderate rain is the most severe precipitation observed during 66% of those days with precipitation. It is most likely around May 31, when it is observed during 50% of all days.
Light rain is the most severe precipitation observed during 16% of those days with precipitation. It is most likely around May 29, when it is observed during 13% of all days.
The likelihood of snow falling is highest around May 1, occurring in 10% of days.
Either snow rarely accumulates at this location in May or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 66% (mildly humid) to 96% (very humid) over the course of a typical May, rarely dropping below 52% (mildly humid) and reaching as high as 100% (very humid).
The air is driest around May 11, at which time the relative humidity drops below 74% (humid) three days out of four; it is most humid around May 30, rising above 94% (very humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a typical May, the dew point typically varies from 36°F (dry) to 48°F (dry) and is rarely below 28°F (dry) or above 54°F (very comfortable).
Over the course of May typical wind speeds vary from 5 mph to 21 mph (light breeze to fresh breeze), rarely exceeding 30 mph (strong breeze).
The highest average wind speed of 14 mph (moderate breeze) occurs around May 1, at which time the average daily maximum wind speed is 21 mph (fresh breeze).
The lowest average wind speed of 13 mph (moderate breeze) occurs around May 29, at which time the average daily maximum wind speed is 19 mph (fresh breeze).