How the weather can affect your hay fever

Pollen affects many millions of people each year. These tiny grains are known to trigger an allergic reaction known as hay fever, and even asthma attacks in susceptible people.

An allergy to grass pollen is the most common, affecting up to 95 per cent of hay fever sufferers.

Pollen is the reproductive substance produced by the male parts of plants and trees.

The weather is linked closely to the pollen level. Wind, rain, humidity, temperature and sunshine can determine how the pollen is spread around. Grass and tree pollen are mainly a problem in the spring and summer months. Weed pollen can extend the pollen season into the early autumn.

Meteorological services provide daily forecasts of pollen concentrations known as “pollen counts”.

The pollen count measures how many grains of pollen are present in a cubic metre of air. Pollen concentration is also dependent on atmospheric pressure. If there are deep convective clouds, visually associated with low pressure, or unstable air masses, the pollen concentration will be relatively low because the grains will have a tendency to ascend to high altitudes inside the clouds.

Paradoxically, Cumulonimbus (storm clouds), can suck in pollen grains, transport them over a large distance and eventually deposit them in shafts of rain in high concentrations.

If however, a temperature inversion exists in the atmosphere, where the temperature increases with altitude (typically associated with areas of high pressure), and there are low level layer (stratus) clouds, or flattened cumulus clouds present, the pollen grains will be trapped in a thick layer close to the ground.

Conditions tend to be optimal for high pollen counts when the weather is dry, warm and windy. However, pollen levels are likely to decrease if very high temperatures are prolonged.

Tree pollen grains that have been found in cores taken from bogs can yield evidence about past climates, stretching back for many thousands of years.

Perusal of Wick’s historic record for mean air temperature for May showed that May 2025 was the coolest since that of 2023. However, a closer look at the archive confirmed that it is currently the 6th mildest in a series commencing from 1910.

In terms of precipitation, May 2025 was the driest since that of 2017, and is presently the 22nd least wet in a series stretching back to 1910.

Wick’s mean air temperature for spring 2025 was 8.50C (47.30F). The burgh’s mean air temperature for spring in terms of the averaging period 1991-2020 is 7.08C (44.74F).

Spring 2025 was Wick’s driest since that of 2020, and is currently the 5th most dry in a series starting from 1871.

The rainfall total for the period was 89.8mm (3.54 inches).

The town’s long-term average quantity for spring is presently 154.06mm (6.07 inches).

Wick’s mean air temperature for May 2025 was 9.92C (49.86F). The long-term average is 8.77C (47.79F).

Wick’s average daily maximum air temperature for May 2025 was 14.02C (57.24F). The current long-term average for May is 12.02C (53.64F).

Highest maximum was 17.5C (63.5F), recorded on May 9. Lowest maximum was 9.0C (48.2F), witnessed on May 3.

Wick’s average daily minimum air temperature for May 2025 was 5.82C (42.48F). The long-term average for the month in terms of the current 30-year averaging period is 5.52C (41.94F). Highest daily minimum was 10.8C (51.4F), observed on May 25. Lowest ambient temperature was 1.2C (34.2F), noted on May 6.

The temperature fell to 0.0C (32.0F) or lower at 5cm over the grass on six dates. The lowest temperature recorded over the grass was minus 1.7C (28.9F), on May 22.

Precipitation occurred on 21 dates. The total for the month was 28.8mm (1.33 inches), or 57.8 per cent of the long-term average for May. The wettest day was May 24. The amount recorded for the 24 hours commencing 9am (GMT) was 7.0mm (0.28 of an inch).

May 2025 experienced no “days of gale”. However, wind velocities reached or surpassed gale force 8, (39.0mph/33.9knots), on three dates.

The strongest wind velocity was observed during the hour ending 10am (GMT) on May 25 when a force 6 west-north-west wind gusted up to 44.9mph/39.0knots, gale force 8 on the Beaufort scale.

A parhelion, also known as a “mock sun” was an optical phenomenon witnessed at sunset on May 28.

Do you want to respond to this article? If so, click here to submit your thoughts and they may be published in print.