Until now, I always thought the notion of the "dog days" rather strange. "Dog days", you may remember, was the name given by the ancient Romans to the hottest period of the year, traditionally the 40 days from July 3rd to August 11th.
It was during this regular annual heatwave, the caniculares dies, that dogs in the street, it was said, were most likely to go mad. And from a human viewpoint, it was the doldrums of the year, a period when the Roman population was debilitated, and had neither the inclination nor the nerve to embark on any worthwhile enterprise.
But the dog days make no sense in an Irish context. If a few warm, sunny days should come along in mid-July, debilitation or lethargy are nowhere to be seen; there is exuberant euphoria, as the whole country goes en fete to celebrate this rare anomaly.
The only complaint you may hear is that it happens all too seldom, and that there is no chance it will last.
But here in Germany, the dog days are self-evident. The weather now is very warm, but it is not the heat that overwhelms: it is the humidity.
With no wind to stir the atmospheric pot, the moisture continually evaporating from the copious Rhine lies stagnant in the surface layers of air; one constantly perspires, all energy is gone, and although a thunderstorm most evenings may clear the air a little for a while, the atmosphere soon returns to its sticky, seeping, sultry, summer norm.
The Romans, of course, thought they knew the reason for their seasonal discomfort. They noticed that around this time of year, Sirius, the Dog Star, the brightest star in all the sky, rises and sets with the sun.
Not unreasonably, they assumed it was the radiant power of this star, added to that of the sun, that provided the extra heat to make July and August in Rome unbearable.
We know now that even all the stars together radiate in our direction only a tiny fraction of the amount of energy we receive daily from the sun, and that a single star could have no effect on our weather. It is hot because the Earth, like a vast storage heater, has retained much of the solar warmth it absorbed in early summer, and is still, on average, warmer than the air above it.
There is a net flow of heat from ground to air in the northern hemisphere, and for a few weeks yet, the average temperature of the lower atmosphere will continue to increase.