Climatic data are available for Roaringwater Bay, as Sherkin Island Marine Station has maintained meteorological records since July 1972. The area has a mild, moist, Atlantic climate, with strong winds, especially during winter months. There are few frosts, and snow is almost unknown, at least at sea level. Rainfall is high, fed for much of the year by low-pressure weather systems over the Atlantic, and dry spells (at least 15 days with less than 1.0 mm of rain) are infrequent. Absolute drought (at least 15 days with less than 0.2 mm of rain) does occur, but never for more than a month at a time (Palmer 1986). Nevertheless, the wind and relatively high sunshine levels have a drying effect on the landscape and vegetation. During the summer months, rocky ground and south-facing slopes dry out, creating the conditions favoured by plants of more southern affinity.

The rain, as in much of Ireland, is not generally heavy but consists of falls of low intensity over extended periods -the 'soft' weather of country people. Annual rainfall recorded on Sherkin ranges from 910.0 mm (1975) to 1392.4 mm (1982), with an average of 1124.8 mm over the years 1972-84. December is the wettest month, with an average rainfall of 136.8 mm; April, with an average of 45.8 mm, is the driest month (Palmer 1986). During the last decade this pattern of wet and dry months has become more erratic. The high rainfall and frequent mists are favourable to plant growth. It has been said that the weather in western Ireland consists of gales interspersed with windy periods. The worst winds come during the winter months, but summer gales are frequent and can do considerable damage to plants. The flowers and fruits of plants, especially on exposed coasts, are often brown and withered after a period of salt-laden Atlantic winds.

The Atlantic Ocean, together with warm currents derived from the North Atlantic Drift, has a moderating effect on the temperature of coastal areas such as Roaringwater Bay, creating few extremes of climate in either winter or summer. During the period 1975-84 the average air temperature in January and February, the coldest months, was 6.7C; the average temperature in August, the warmest month, was 15.5C (Palmer 1995b). Between 1975 and 1994, rarely did the air temperatures fall to 0C on more than 10 days a year. The last 10 years have seen far fewer frosts (for example, no air frost at all was recorded in 1989), whereas in 1978 and 1979 there were 22 and 26 days of air frost respectively. During the last 20 years, the temperature rarely fell below -4C, although -7.7C was recorded in January 1979. Conversely, the temperature in summer rarely rose above 20C, although 26.4C was recorded during the famous hot August of 1976.

Sunshine levels in Roaringwater Bay are high -coastal areas usually receive greater amounts of sunshine than those inland. May is by far the sunniest month, but high levels of daily sunshine may be enjoyed from early April through to the end of August (Palmer 1995a). During the last 10 years at least, May has been a particularly sunny and dry month.

Source: The Wild Plants of Sherkin, Cape Clear and adjacent Islands of West Cork. Ed. John Akeroyd. Sherkin Island Marine Station, Sherkin Island, West Cork, 1996.

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