The author: Making observation of air temperature on thermometers housed in a Stevenson screen.

Llansadwrn (Anglesey) Weather


from the observer's notebook

Logo: Llansadwrn Weather - Melin Llynnon, Ynys Môn

Airfrosts in April

Several places inland, and at notorious frost hollows, have had airfrost this month. On the night of the 8/9th minimum temperatures between -2C and -4C (Redhill frost hollow -7C) were seen in England whereas, around the coasts and in the north, temperatures kept above freezing. Altitude makes a difference too so that in the mountains -3C was recorded at Capel Curig. Here, at 351 ft, we had 1.0C in the air and -3.3C on the grass. On the 9/10th we did have an airfrost of -1.3C, the first since 1990 that had 3, with -6.0C on the grass. Nearer the coast Valley saw 0C and in the mountains Capel Curig had -5C. Llanbedr (Gwynedd) saw -3C while Hawarden (Flintshire) was one of the coldest places with -8C. The Midlands of England saw between -2C to -3C. Frost occurred on the south coast of England too with Exeter and Southampton having -1C. It was warmer in the north with Stornoway (Western Isles) having a minimum of +7C and Kirkwall +3C.

Click for graph of airfrosts at Llansadwrn: © 2003 D.Perkins.

Airfrosts were frequent here in the 12 years 1979 - 1990 (average 2.2) but have been fewer in recent years 1980 - 2002 (average 0.5). This month's frost is the first in April since 1990 that had 3. Another indication of the recent warming trend.

Click for graph of average number of airfrosts each month at Llansadwrn: © 2003 D.Perkins.

February with an average of 7.7 days of airfrost is the frostiest month in the year closely followed by December with 6.7 and January 7.2. No airfrost has been recorded from June to September and few only a few in May with an average of 0.3 and October 0.1 days. March has an average of 3.2 and November 1.8 days. Airfrost in April is not unexpected; it has an average of 1.3 days a year. There was no airfrost in some years (1991 - 1994, 1997, 1998 and 2000 - 2002) while in others there have been up to 4 (1979, 1984 and 1985).

Flowers of this Rhododendron were scorched by airfrost on 9/10th April; photo taken on 12 April 2003.

Hardy plants usually have no problem with late frosts but if new growth has started, or flowers developed in early warmth as in this year, some damage can occur. If annual garden plants are planted out too early, or not properly hardened off, they too can suffer and even die. With fruit trees coming into blossom at this time of year late airfrosts are bad news for fruit growers. Crops can be seriously reduced by late frosts.

In France frosts, between 7 - 11 April 2003, damaged up to 50% of the grape vines and effects were the worst seen in 70 years . Grape vine buds break in mid- to S France in April and the new shoots are vulnerable to late frost. Chardonnay grapes used in Champagne production, were the worst affected (estimated 80% vines). Overall a total of 50% damage was estimated. In N France, and Britain, the buds break later and may have escaped damage.

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These pages are designed and written by Donald Perkins © 1998 - 2003

Document dated 10 April 2003

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