Wick's weather for May highlights the changing seasons
Weather Watch by Keith Banks
The changing seasons, with their varying lengths of day, and night, together with the differing types of weather, arise from the changing aspect of the Earth, relative to the Sun, in its yearly revolution.
Caithness experiences all four seasons – the reason for this is the "tilt" of the Earth. The Earth's axis always points in the same direction in space; inclined at an angle of 66.5 degrees to an abstract and imaginary flat, disc shaped surface called the "Plane of the Ecliptic" that contains the Earth's orbit around the Sun.
In the Northern Hemisphere winter, the Earth is tilted away from the Sun. Hence, at the winter solstice, (December 22), all places within the Arctic Circle, latitude 66.5 degrees N, the Sun is not above the horizon at any time during the 24 hours, and all other places in the Northern Hemisphere also have their shortest day.
Conversely, at the summer solstice, June 21, places within the Arctic Circle experience their longest day.
Crucially, the changing aspect of the Earth, relative to the Sun is the reason why the midday Sun is higher in the sky in the summer months. The difference between mid summer and mid winter is 47 degrees. Therefore, the heating effect of the Sun's rays are greatest in summer because they are spread over a smaller area.
May 2021 was Wick's coldest since that of 1996. Perusal of the town's historic record for mean air temperature for a series of Mays commencing from 1910, shows that May 2021 is currently the 11th most cold. In terms of precipitation, May 2021 was the least wet since that of 2018, and is presently the 41st driest in a series commencing from 1910.
Spring 2021 was Wick's coolest since that of 2013. The mean air temperature was 6.24C (43.23F). The town's mean air temperature for spring in terms of the averaging period 1981-2010 is 6.68C (44.02F).
This spring was Wick's most wet since that of 2019. The precipitation total was 129.2mm (5.10 inches). The long-term average quantity, for spring, is currently 165.0mm (6.50 inches).
Meteorological spring is the calendar period beginning March 1 and ending May 31.
Wick's mean air temperature for May 2021 was 7.31C (45.16F). The long-term average for May, in terms of the averaging period 1981-2010 is 8.60c (47.48F).
Wick's average maximum daytime air temperature for May 2021 was 10.30C (50.54F), 1.50C lower than the current long-term average for May. Highest maximum was 14.2C (57.6F), observed on May 31. The lowest maximum was 7.3C (45.10F), recorded on May 2.
Wick's average overnight minimum air temperature for May 2021 was 4.32C (39.78F). The current long-term average for May is 5.40C (41.72F).
Highest overnight minimum air temperature was 8.1C (46.6F), logged on May 24 and 25 respectively.
There were three air frosts. The lowest ambient temperature was minus 1.6C (29.1F), witnessed on May 8.
A ground frost was observed on 10 dates; the same number as logged for May 2020. Lowest temperature recorded at 5cm over the grass was minus 4.1C (24.6F), on May 3.
Precipitation was measurable on 22 dates. The total for the month was 39.4mm (1.55 inches), or 81.1 per cent of the long-term average for May. The wettest day was May 23. The amount for the 24 hours commencing 9am (GMT) was 8.4mm (0.33 of an inch).
Between May 4 and 6, graupel, and wet snow, were observed during showers.
The strongest wind velocity was observed during the hour ending 11am (GMT), on May 24, when a force 6 north-easterly wind gusted up to 40mph/34.8knots, gale force 8 on the Beaufort scale.