by Janet Spencer

Heat waves are the single deadliest weather phenomena in the U.S., killing more people than hurricanes, wildfire, blizzards, or floods. Come along with Tidbits as we deal with heat waves!


• In 2003, Europe’s worst heat wave in 500 years afflicted the continent with temperatures reaching a high of 115°F (46°C) in places. Throughout August, temperatures averaged 20 to 30% higher than normal. Over 30,000 people died across the continent. The populace was unaccustomed to dealing with such heat and there was little they could do to adapt on such short notice. Most vulnerable were elderly childless women who lived alone.

• Particularly hard hit was France, who suffered an estimated 15,000 casualties. Paris was badly affected. The hospitals and morgues were so overwhelmed that they purchased refrigerated food trucks and rented a refrigerated warehouse to store the bodies until they could be buried.

• About 80% of buildings in Paris have zinc roofs, amounting to over 100,000 buildings. Zinc roofs are extremely picturesque, but they also heat up like a sizzling griddle on hot days. People living on the top floors of buildings with zinc roofs bore the biggest brunt of the heat.


• Another contributing factor in the high death rate in 2003 was that Paris has very few urban trees, with only 9% of the city streets shaded by a tree canopy, compared to 18% in Boston, Massachusetts, and 29% in Oslo, Norway.

• During a Texas heat wave in 2011, drought and heat killed off an estimated 10% of all urban trees statewide.

• In Austin, Texas, “tree inequality” is more pronounced than in most cities, with rich neighborhoods having many large shady trees, and poorer neighborhoods having few.

• When officials in Seoul, South Korea restored a stream that ran through the middle of the city, and planted numerous shade trees, the temperature of the surrounding neighborhoods dropped by ten degrees.

• The city of Curitiba, Brazil, (pop. 3.8 million) is known as “the greenest city on Earth” because they’ve dedicated over 24 square yards (20 sq. m) of green space per citizen, whereas Buenos Aries, Argentina, by contrast, has only two. Many other cities have virtually none.


• It’s estimated that 30 million people in the U.S. live in areas of extreme heat, defined as a mean annual temperature above 85°F. (29°C) Unprotected (un-air conditioned) humans die if the temperature fails to fall below 104°F (40°C) at night for a prolonged time, giving them a chance to recover.


• A camel can go eight to ten days without water during hot seasons, losing up to a third of its weight by dehydration. They’ve also adapted to be able to drink salt water that’s even saltier than sea water, and to eat salty plants other animals ignore.

• An ant that lives in the Sahara desert has specialized skills to survive the heat. The ant only goes out when it’s too hot out for ant-eating lizards to be out, which means temperatures of 122°F (50°C) or so. They have long legs and run fast over super-heated sand, covering up to a yard per second. This is equal to a human running about 450 mph (724 kph). The ant sports silver-colored hairs on its body, which reflect heat away. The ant can only be exposed to the heat for a few minutes before returning to the cool relief of underground burrows.

• Pacific salmon require cold water in mountain streams, and cool ocean water. They prefer water that is 58°F (14°C) or less. When the water temperature rises above 59°F, they begin to struggle. Diseases become more prevalent and they succumb to predation at higher rates. If the water temperature tops 70°F (21°C), it forms an impenetrable barrier that salmon cannot navigate through. When heat waves in California in 2011 raised the temperature of salmon-filled rivers beyond their ability to survive, wildlife officials caught the fish and taxied them upstream to their spawning grounds in tanker trucks.

• Many arctic birds have black feathers, the better to absorb heat from the sun. However, when temperatures rise, they easily become overheated.

• Bumblebees are disappearing from areas eight times faster than they are colonizing other areas because of the heat.


• Although extra carbon dioxide in the atmosphere is somewhat beneficial to plants, the heat caused by excess carbon dioxide is far more detrimental than beneficial. Leaves are unable to photosynthesize at temperatures of 116°F (47°C) or above.

• Most plants are about 97% water, compared to humans which are about 60% water. When plants are subjected to inordinate heat, it messes with their metabolism just like it does ours, by raising it and increasing their need for water. The hotter it gets, the more water they need. To keep themselves cool, their leaves “sweat”, giving off water in what’s called “transpiration.” Most plants transpire their weight in water every day during normal temperatures, which would be equal to humans needing to drink 20 gallons (76 l) of water a day. If the temperature rises from 70 to 95°F (25 to 35°C), the plant needs twice the amount of water to survive.

• A one-acre plot of corn in Iowa can sweat 4,000 gallons (15,150 l) a day on a typical summer day, enough to fill a typical backyard swimming pool.

• Heat can promote the growth of a deadly fungus that grows on corn.

• Excess heat destroys the pollen tubes of corn plants, preventing fertilization which thwarts formation of the ear of corn.

• Heat changes the timing of blooms of many species of flowering plants, often making the plant miss the peak season for pollinators.


• A heat wave off the coast of California in 2013 resulted in the wholesale destruction of the entire local population of sea stars, a type of starfish. Sea stars are one of the primary predators of purple sea urchins. With the absence of sea stars, the sea urchin population exploded. Sea urchins eat kelp. Entire kelp forests, once vibrantly full of myriad sea creatures, vanished within weeks.

The Mediterranean Sea is particularly vulnerable to heat spikes, with the water sometimes rising by 11°F (6°C) above normal, scorching sea life. These events have been likened to underwater wildfires.