Thursday, January 10, 2008

Weather extremes

Which parts of the USA have the highest annual average temperature?

According to the National Climatic Data Center, the warmest parts of the USA are the Florida Keys, where the annual average temperature is about 77.7°. Southeast Florida, including Miami, is also warm at 75.4°. Those spots are even warmer than Oahu in Hawaii, where the temperature averages 74.4°. Compare that to the coldest spot, far northern Alaska, where the average temperature is a frigid 14.5°.

What’s the lowest temperature ever recorded in the USA?

It was –79.8°F (rounded off to –80°F) that was observed at Prospect Creek Camp in northern Alaska on Jan. 23, 1971. The Prospect Creek Camp is located along the Alaska Pipeline, about 20 miles north of the Arctic Circle. The lowest temperature ever recorded in the lower 48 States was –69.7°F (rounded off to –70°F) at Rogers Pass, Mont., on Jan. 20, 1954.

Which U.S. cities have the highest heat indexes each summer?

The heat index, sometimes referred to as "apparent temperature," is a measure of how hot it feels when relative humidity is combined with the actual air temperature. Although the National Climatic Data Center does not archive heat index values, past studies that looked at differences in apparent temperature across the USA can help answer this question. In one study, Phoenix came out tops on the list, because of its extremely hot temperatures, not because of high humidity.

In some cases, cities with lower temperatures but higher humidity — such as Waco, Texas, and Key West — top other places that have higher temperatures.

What's the coldest and driest place in the USA?

Barrow, Alaska, which averages less than 5 inches of precipitation and an annual average temperature of about 10°F, is the coldest and driest place in the USA. In the lower 48 states, one of the coldest and driest places is Gunnison, Colo., which averages less than a foot of precipitation each year and has an annual average temperature of about 37°F.

At the other end of the spectrum, the warmest and wettest place in the country is Hawaii, which averages over 100 inches of precipitation and temperatures greater than 65°F annually. In the lower 48 states, the Gulf Coast and parts of Florida average between 70 and 100 inches of precipitation and temperatures greater than 65°F annually.

What is the hottest summer in U.S. history?

The National Climatic Data Center has reported that July was the second-warmest month on record, and June the second-warmest June. The warmest summers in U.S. history were during the Dust Bowl years of the mid-30s: 1936 was the hottest, with an average of 74.7°F, and 1934 the second-hottest at 74.3°F.

The average U.S. summer temperature is 72.1°F. The coolest summer on record was in 1915, when the nation's temperature for June, July and August measured 69.7°F, the only sub-70°F summer since records began in 1895.

What states usually have the coolest weather in the summer?

With average temperatures that range from the upper 40s to upper 50s, Alaska is the coolest U.S. state in July, according to the National Climatic Data Center. (July is typically the USA’s hottest summer month.) Other cool states in July are in the Northwest, such as Washington, Oregon, Idaho, Montana, Wyoming and Idaho. The coldest parts of the Northwest are in western Wyoming and the Cascade Mountains of Washington, where average July temperatures are in the upper 50s.

What's the highest temperature ever recorded in the Southern Hemisphere?

According to the National Climatic Data Center, Cloncurry, Queensland, in Australia, holds the high-temperature record in the Southern Hemisphere. The mercury there topped out at 128°F on Jan. 16, 1889. Remember that January is the middle of summer and typically one of the hottest months in the Southern Hemisphere.

Because the method of measuring temperature at that time was not consistent with modern methods, the Australian record using standard equipment is 123°F, recorded at Oodnadatta in 1960.

What are the coldest cities in the USA?

The coldest major city in the USA is Minneapolis, which has an annual average temperature of 45.2 F. However, several other smaller cities are much colder, including Fairbanks, Alaska (26.7 F), Anchorage (36.2 F), International Falls, Minn. (37.4 F), Duluth, Minn., (39.1 F), and Caribou, Maine (39.2 F). In Fairbanks, for example, the average daily high temperature in January is -0.3ºF.

Which counties in the USA receive the most storm warnings issued by the National Weather Service?

A tally of all flash flood, severe thunderstorm and tornado warnings between 2001 and 2005 show that Pima County, Ariz., (which includes Tucson) had the most warnings with a total of 404. San Bernardino County, Calif., (east of Los Angeles) was second with 320, followed by Harris County, Texas, (which includes Houston) with 281.

What was the world's all-time record highest temperature? When did it occur?

The world's highest recorded temperature -- 136°F -- occurred in Al Aziziyah, Libya, on September 13, 1922. Al Aziziyah is located 20 miles south of Tripoli. Many of the world's highest temperatures have been recorded in north Africa, although Death Valley, California, recorded the world's second-highest temperature of 134°F on July 10, 1913.

Which states receive the most sunshine each year?

While Florida proclaims itself "the Sunshine State," it might be more appropriately named the "partly cloudy" state. Five other states, Arizona, California, Nevada, New Mexico and Texas, catch more rays than Florida, according to the National Weather Service.

It should be kept in mind that, despite the cloud cover that results from Florida's proximity to water, Florida's sunshine is very strong because the state is in the subtropics. Rays from the sun arrive at a steep angle, bringing a high degree of ultraviolet radiation. That could be a factor in Florida's high rate of skin cancer. It ranks in the top five nationally, according to the Centers for Disease Control and Prevention.

What is the greatest wind speed ever measured in a hurricane?

During the New England hurricane of September 21, 1938, winds gusted to 186 mph at Blue Hill Observatory in Massachusetts. Many instruments break at these speeds, so higher winds in other hurricanes may have gone unreported. About 4,500 feet above sea level, a parachute-borne instrument recorded winds of 234 mph in 2003's Hurricane Isabel, according to the National Oceanographic and Atmospheric Administration's Tropical Prediction Center.

Surface wind reports can't be easily gathered at sea or on land during hurricanes, so many wind estimates for intense hurricanes are extrapolated to sea level from winds recorded at flight levels of around 10,000 feet. At this height, hurricane winds are typically 5% to 10% stronger than they are on the ground, where friction slows them down.

What are the coldest and warmest temperatures ever recorded in California?

Like so many other categories, the weather extremes in California are quite diverse. The record high temperature is a sizzling 134°F, recorded on July 10, 1913, in Death Valley (elevation: 178 feet below sea level). This is the North American record and is just shy of the world record of 136°F in Libya.

On the cool side, the mercury plunged to -45°F in Boca on January 20, 1937. Boca is located at an elevation of 5,532 feet, a few miles north of I-80 on the east slopes of the Sierra Nevada.

The difference between these extremes is a noteworthy 179°F and is mostly a function of both locations being distant from the moderating influences of the Pacific Ocean.

However, this is not the biggest difference between a state’s extreme high and low temperature readings. That honor goes to Montana, with a range of 187°F. The state's record minimum of -70°F is the lowest in the continental 48 states and its record high is 117°F.

The narrowest extreme temperature range in the continental 48 is 111°F in Florida, based on a record high of 109°F and a record low of -2°F. However if Hawaii is included, the range is just 88°F, due to the moderating influence of the tropical water that surround the islands.

Why is Saranac Lake, N.Y., consistently one of the coldest spots in the contiguous USA ?

To be one of the coldest locations in the contiguous USA requires several physical attributes, each of which Saranac Lake possesses. Temperatures decrease with both latitude and elevation, so cold locations such as Saranac Lake tend to be located in mountainous regions of the northern USA. Saranac Lake's inland location, away from the moderating effects of the Atlantic Ocean, also contributes to its coldness.

Two other features make Saranac Lake stand out from any number of northern inland mountainous locations. The first is meteorological. The town lies in a high-elevation valley. Thus cold air, which is more dense, flows down the surrounding mountain slopes and accumulates over Saranac Lake. The second is serendipitous. There happens to be an airport weather station that reports daily temperatures at Saranac Lake. Relatively few airports are located in this type of topography.

What are the sunniest and cloudiest cities in the USA?

One way to measure this is by the percentage of the possible sunshine that a city receives each year. The sunniest city in the United States is Yuma, Arizona, which receives 90% of possible sunshine.

The next 4 sunny cities are: Redding, Calif.; Flagstaff; Phoenix; and Las Vegas.

The cloudiest city is Juneau, Alaska, which receives only 30% of the annual possible sunshine. Other cloudy cities are Quillayute, Washington; Elkins, West Virginia; Hilo, Hawaii; and Anchorage.

What is the largest amount of snow ever documented in a year?

During the Western snowfall season that began July 1, 1998, and ended June 30, 1999, Mt. Baker Ski Area in northwestern Washington set the US record for most snow in a year with 1,140 inches. The ski area is at 4,200 feet in Washington's Cascade mountain range. The previous record of 1,122 inches was set at nearby Mt. Rainier during the 1971-1972 snowfall season. Read the story: Mt. Baker snowfall record sticks.

The Mt. Baker Ski Area snowfall total also is the highest amount ever recorded in a single year anywhere. That qualifies it as a world record as well, but only in theory since there are no formal records of seasonal snowfall kept outside the USA to compare it to.

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