During our winter season, you can be pretty well assured that the world's lowest temperature, for any given day, will occur in Russia, the US, Canada or Greenland. While it's possible for other countries or territories to go low, it doesn't often happen. In general, in winter, the lowest temperatures occur where it's darkest. However, in summer, the highest temperatures do not occur where there's the most light. Even though temperatures in July and August can exceed 90 degrees F in central Alaska and even in parts of Siberia, in summertime, it's the subtropics and mid latitudes that really sizzle.

Extreme high and extreme low temperatures have at least one ingredient in common, clear skies. The world's daily maximum and minimum temperatures are certain to be found where ever clear skies prevail. In the winter and summer months, the global highs and low usually occur in opposite hemispheres. The highest temperatures occur in arid areas where sunny weather and dry air allow for maximum heating, and the lowest temperatures occur where clear skies at night permit the air to cool by the process of radiation cooling - heat is radiated away from the surface and into space.

The transition from the regions where the world's highest temperatures are observed in spring to where they're observed in summer is often rather gradual. From March through May, the highest temperatures generally occur on the Indian sub continent, in the savanna areas of north central Africa and on the Arabian Peninsula. For example the high temperature on May 20 was119 F in Fahud, Oman. When monsoonal rains begin to drench India in late May, this area won't record another world daily maximum until sometime in autumn. From about mid May until the end of September, the hottest temperatures are often recorded in the mid latitudes - north of 23 1/2 degrees north latitude.

One of the world's hot spots during mid and late summer is the southwestern US (including Mexico). Another hot spot is the region around the Persian Gulf, the countries of Saudi Arabia, Iraq, Iran, Kuwait, the United Arab Emirates, and Oman. In addition, the area to the east of the Mediterranean Sea, Syria, Jordan and Israel, can be hot enough to singe your hair (well almost) during the summer months. All of these countries have recorded maximum temperatures of over 120 F - the actual surface temperatures may surpass 150 F. On the Arabian Peninsula, beginning in late April, the desert air can heat up to well over 100 degrees for weeks on end. The only time that it's not unmercifully hot is if a layer of clouds keeps the Sun at bay. The Sahara Desert in northern Africa (Algeria, Tunisia, Libya, Egypt, and Sudan) is another place that can be like an inferno. The all time world record temperature of 136 F was observed in Libya on September 13, 1922.

In the summer of 2001, Saudi Arabia and the US (Death Valley) most often recorded the highest daily global temperatures. Death Valley, one of the world's more appropriately named features, can be like a sauna during the summer. The Western Hemisphere's highest temperature (134 F) was recorded there in 1913. In fact, the average July maximum temperature is 116 F, and in 1917, there were 43 consecutive days with a maximum temperature above 120! This year, from the 1st of June until now, the high daily temperature in the US has been observed at Death Valley over 80% of the time - the highest temperature was 127 F on July 3. A combination of clear desert skies, light winds and below sea level elevations set the stage for high heat. The temperature will drop some at night, but when it's over 120 F during the day, the nighttime temperature may fail to fall below 100 F!

The valley floor can be heated to near inhumane temperatures because as air descends into the approximately 140 mile long and 16 mile wide valley (at its widest point), it compresses and dries, and because Death Valley lies about 280 feet below sea level, the compression results in even hotter temperatures. A parcel of air moving from a layer of low pressure to a layer of high pressure will compress and warm, much as a tire is warmed when pumped with air. The rate at which the temperature will change as a parcel of air moves vertically is everywhere the same, as long as condensation or evaporation do not occur. This rate, termed the dry adiabatic lapse rate, is 5.5oF per 1000 ft. Thus, on a day in mid summer, if the air temperature on top of the nearly 5,000 ft range forming the western border of Death Valley (the Panamint Range) is 80 F, for example, it'll warm by about 30 degrees as it descends to the bottom of the Death Valley.

In regards to the world's daily minimum temperatures, the transition from where the world's lows are recorded in spring, Siberia, Alaska or the territories of northern Canada, to where they're recorded in summer can be fairly abrupt. Usually, the transition occurs over a few week period in May and June. For instance, the world's lowest temperature on May 20 was 1 degree F in Anaktuvuk Pass, Alaska, but a week later the low temperature was observed in South America. By June, most of the Northern Hemisphere's seasonal snow has melted and with sunlight bathing the surface all day, the minimum temperatures are nearly always above zero degrees F. Even the air above the huge Greenland Ice Sheet has warmed up enough so that minimum temperatures don't often fall below zero F.

By mid June, excluding Antarctica, the lowest daily worldwide temperatures typically are recorded in the Southern Hemisphere, where winter is just starting. Even though the southern tip of South America is in the mid latitudes (55 degrees) and is more than 2,000 miles away from the source area for the most frigid air in Antarctica, cold air from the bottom of the world can be pushed northward into Argentina and all the way to the sub tropics. The Tierra del Fuego area at the extreme tip of Argentina and Chile and the Patagonia region of southern Argentina are near enough to Antarctica to be routinely subjected to icy blasts during the winter season.

The world's lowest temperatures, during the Northern Hemisphere summer, occur most often in the South American countries of Argentina, Bolivia and Chile. Yes, Chile can be chilly. In the Patagonia region of Argentina, temperatures fall below 0 F on some mornings in July and August. However, Patagonia can be cloudy for long stretches of time during the summer season, and when it's cloudy there, temperatures are apt to be lower wherever else in South America that the skies are clear. In Bolivia, morning temperatures often drop to the single digits (F), but the cool temperatures are attributable to the altitude rather than the latitude. Eastern Bolivia is in the Andes Mountains, and many cities lie at an elevation of more than 10,000 feet. Even the capital city of La Paz (16 degrees south latitude) is more than 11,000 feet above sea level.

A sample of recent observations shows that on August 29, the world's high of 120 F occurred in Death Valley and the world's low of13 F occurred in Charana, Bolivia. On September 3, the world's high temperature, was 118 F in Al Makakah, Saudi Arabia (it was a mere 114 F in Death Valley), and the world's lowest temperature was 18 F in Charana, Bolivia. This was one of the highest daily minimum temperatures for all of 2001. On September 4, the high temperature was 118 F in Kuwait City, Kuwait (Death Valley wimped out with a 109 F reading), and the low temperature in the world was 4 F in Esperanza, Argentina.