August marks the beginning of autumn, according to the Celtic calendar 

Met Éireann says it uses 'meteorological seasons to divide the year into four seasons of equal length [three months each]' as it 'helps enormously in the calculation and provisional of seasonal statistics'. Picture: Larry Cummins

While most believe summer ends in August, the Celtic calendar shows the season ending in July, therefore making Tuesday the 'traditional' beginning of autumn.

According to Met Éireann, the Celtic calendar — with seasons Imbolc (spring), Bealtaine (summer), Lughnassa (autumn) and Samhain (winter) — differs from the meteorological calendar which is used by the forecaster.