Far away from the riots and the homicides, the heat still gets to us, stoking politely suppressed emotions into flames - and nowhere is this more true than in the urban furnace of the traffic jam. In 1986, two psychologists, Douglas Kenrick and SW Macfarlane, devised an experiment few might have dared conduct on a clogged British A-road in recent days. In a range of weather conditions, they arranged for a car to pull up repeatedly at a set of traffic lights and refuse to budge when they turned green. As frustration crackled through the vehicles stacking up behind, they got out their clipboards and measured how much time elapsed until another driver sounded their horn, and how many times they did so. They found a direct, linear relationship between the temperature outside and the intensity and alacrity of horn-honking.
Similar situations occur in other countries where the heat comes as a disorienting surprise.
One psychologist at Uppsala University in Sweden, AE af Wahlberg, found a greater tendency for Swedish buses to crash on hot days. There was more going on, he suggested, than the mere fact that the sun brings more people out onto the roads. These are not problems that we, as a nation, are accustomed to confronting, conditioned as we to cold-weather complaints. But after the events of this week - when, in the heat of a summer night, deeply felt tensions in Oldham ignited into violence, we might be advised to think again.