METEOROLOGISTS base their concept of the seasons on the average temperature measured at these latitudes. They designate the three coldest months of the year as, "winter" and the three warmest ones as "summer", so almost by default, the three autumn months turn out to be September, October and November. By this reckoning autumn 1996 began yesterday, and September provides a gentle introduction into the new season. According to Longfellow, it is the time when
With a sober gladness the old year takes lip
His bright inheritance of golden fruits,
And pomp and pageant fill the splendid scene.
Be that as it may, September's transitional nature is very evident from the thermometer. On a typical August day, for example, the temperature may climb to about 20; in October, on the other hand, the average maximum is only 14; but September takes the middle ground, with an average daily maximum temperature of around 16 or 17 degrees. On two or three days during the month, the thermometer may top 20, but a temperature of 25C, common enough in August, is very rare indeed.
September nights are cool. Ground frost becomes a common occurrence as the month matures, with the ground temperature slipping below the freezing point on an average of three or four occasions in the second half of the month. The air temperature however - the temperature as measured four feet above the ground - drops below zero only very rarely.
September is neither particularly wet nor very dry. Most places experience between 100 and 150 millimetres of rain, with an extra 50 to 100 millimetres in places some height above sea level. But with the evenings drawing in, we can expect rather less sunshine: 4 or 5 hours per day is the norm for September - about an hour less than the average for August.
Although September is by and large a diffident month that avoids the limelight and the record books, it brought us one of the most vigorous storms of recent memory. The depression associated with Hurricane Debbie reached Ireland on September 16th, 1961, and many of the records for strong winds that were established at that time still stand. The windiest parts of Ireland, our west and northwest coasts, experience an average of 2 to 3 gales in September, which is rather more than the summertime norm but significantly less than the usual for late autumn and winter.