It’s the summer holidays and it’s pouring with rain! What else did you expect from this wonderful country of our? A little bit of hot weather? Well, cast your minds back over the last few years (few months actually, we had a heatwave declared in June!) You can bet your bottom Pound Sterling that with the hot weather comes the inevitable scaremongering from the media that will begin with some websites pondering whether our weather might descend into a “heat wave”. But what exactly is a heat wave? Let’s take a look.
“A heat wave is a prolonged period of excessively hot weather, which may be accompanied by high humidity. There is no universal definition of a heat wave;the term is relative to the usual weather in the area.”
Put simply, a heat wave is a time of higher than average temperatures in an area, but since the climate of two areas may not be the same, there is no single temperature that must be achieved for it to be considered a heat wave. The reccommended definition is that when the daily maximum temperature of more than five days in a row is higher than the average temperature by more than five degrees Celsius.
So how do they happen?
Well, heat waves are usually caused by an area of high pressure where the air and the ground get heated to excess and there is very little to displace the heat, such as cloud cover. A static high pressure area (one that does not move) can create a very persistent heat wave. Hot winds blowing from tropical or desert areas can also contribute to the creation of heat waves, with the warmer air being blown onto an area that is usually cooler, combining with the high pressure area. The “Heat Island” phenomenon caused by large urban areas such as cities can also exacerbate (such a big word, so grown up!) a heat wave and make it worse, due to the prolonged period of heat, cutting down the amount of night time cooling.
What damage can heat waves do?
Medical issues such as Hyperthermia (heat stroke) and Heat rash, among others can be caused by the extreme weather. A usual precaution taken during a heat wave is to set up air conditioned “cooling areas” for the public in most cities. In worst case scenarios heat waves can kill, as seen in the 2003 European heat wave, where around 15,000 people died in France alone. Wildfires can be started in some areas, where the heat affects dry vegetation and causes it to catch alight. In 2003 fires raged through Portugal as a consequence of the heat. Heatwaves can also cause physical damage to infrastructure with pavements and roads melting and buckling due to the heat.
You mentioned 2003 in Europe?
Why yes I did. All good Geographers love a Case Study and this is ours for a Heatwave. In 2003 a heat wave erupted over most of western Europe. You can see the areas affected on the map I’ve included at the end of this post. In 2003, the summer was the hottest on record since at least 1540. This created major health crises in many countries, with France being hit especially hard. This, combined with a drought that caused a major crop shortfall in the South of the continent, caused over 40,000 Europeans to lose their lives. The UK managed to escape the worst, and was brought a short period of relief by Atlantic cyclones, bringing cool, wet weather for a few days before the temperatures started to rise once again. Around 2000 people died in the UK.
Well there you have it. The phenomenon known as a heat wave has been broken down a bit and explained. Now, whenever this rain stops you can understand what all the scary news articles are about! See you all soon for another bit of Geography, Simplified!