Here’s how often temperatures reach 100 degrees

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  • Triple-digit temperatures are most common in the desert Southwest.
  • Temperatures in other surprising cities also reach 100 degrees.
  • Some locations that you might think would see several 100 degree days a year, actually don’t.

The 100 Degrees Club is out of reach for many cities, but others can count on being a member every year.

High temperatures rise beyond the century each summer in some areas of the United States and extreme heat becomes the norm. For some locations, triple-digit heat can last for months, but for others, it has never happened since records began.

Climate and geography can have big impacts on how often cities see temperatures reach 100 degrees. Below, we take a look at some interesting stats on the triple-digit Heat across the Lower 48.

The Desert Southwest is a place where 100 degree heat is more common. Many cities in the West see temperatures above the century mark each year, and this is especially the case in the Desert Southwest.

Las Vegas, Phoenix, and Tucson are all distinguished members of the triple-digit club, as the average number of 100-degree days for all three cities is well over 50 per year. The highest temperature on record in Las Vegas is 117, which has been reached several times, most recently in 2021.

Averages are based on climate data for the period 1991-2020.

Death Valley comes to mind for many when thinking of sweltering conditions because it holds the world record for the highest temperature of 134 degrees, recorded on July 10, 1913.

The average number of 100 degree days hotter per year in Death Valley is 147, just two more than the current record for most such days in Phoenix, which was set in 2020. Last year, temperatures in Death Valley dropped It reached 100 degrees at least 160 times.

(More: Death Valley Heat Records)

Triple-digit temperatures are less common elsewhere in the West. Unsurprisingly, Seattle and Portland, Oregon don’t often have 100 degree days. Seattle has measured a reading of 100 degrees only six times, two of which were during the historic June 2021 heat wave when the highest temperature on record of 107 degrees was reached. Portland also set a new record for hottest temperature during that heat wave when the high reached 117 degrees.

Triple-digit temperatures are more common east of the Cascades; Even sites in Montana get up to 100 degrees from time to time. The 100 hottest days in Missoula, Montana, were 11 in 2007, and in 2022, there were 10 days with a high of at least 100. The highest temperature recorded there is 107.

(More: This is the time when the highs of 90 degrees of the year typically occur)

What is the reason for the heat, or lack thereof, in the West? These very hot conditions are due to a combination of factors, including altitude, humidity, and location.

The southernmost locations in the United States benefit from a higher sun angle, resulting in increased solar radiation. Lower altitudes also tend to experience higher temperatures, as temperatures drop as you move higher in the atmosphere. The air tends to be drier in much of the West in the summer, and dry air is able to heat more easily than humid air.

Temperatures in areas near the West Coast are affected by the cold Pacific Ocean, which reduces the temperature there to 100 degrees.

Triple-digit temperatures are common on the plains. Winds downhill from the Rocky Mountains can help warm temperatures, and the region’s location between the Rocky Mountains and far enough from the Gulf of Mexico can lead to drier air.

The Southern Plains have several cities in the triple-digit club and experience more frequent extreme heat compared to the Northern Plains due to the difference in latitude.

Dallas is one of those cities. The average date of the first 100 degree day is July 3. The year with the highest temperatures of 100 degrees in Dallas was 2011 when highs exceeded the century mark 71 times. That year, an exceptional drought spread throughout the region.

To the southwest in El Paso, Texas, temperatures typically hit triple digits 27 days a year. Farther north in Oklahoma City, there are about 13 days a year when the temperature reaches 100 degrees or higher; Last year, there were 24 such days.

Averages are based on climate data for the period 1991-2020.

The 100 degree mark becomes a little out of reach near the Gulf of Mexico due to increased humidity. Houston typically sees only seven days each year with a temperature of at least 100 degrees. There are fewer hot days in Brownsville, Texas, where the average is two days per year. The highest number recorded in a year is 12 in 2019.

The northern Plains see their share of triple-digit heat, usually when a powerful upper ridge of high pressure builds up across the region.

The highest temperature on record in the North Dakota cities of Bismarck and Fargo is 114 degrees and was recorded in July 1936. Many cities in the central and northern Plains set temperature records and experienced the largest number of 100 degree days during a dust storm. in 1936. North Dakota even reached 121 degrees near Steele on July 6, 1936.

The Midwest can experience 100 degree days. Temperatures can soar to 100 degrees or higher in the Midwest, most often when high pressure dominates the region in the summer with southerly flow.

Sh. St. Louis and Kansas City each typically see about three days of 100 degree temperatures each year. Last year, St. Louis saw seven 100-degree days, while Kansas City saw three.

Most of the region experiences triple-digit heat every few years.

The highest temperature on record in both Chicago and Milwaukee is 105 degrees, recorded on July 24, 1934. Both cities also had 100 hottest days in 1988 — seven in Chicago and six in Milwaukee. Widespread drought occurred in parts of the United States in 1988, contributing to widespread and unusually high temperatures.

Many other Midwestern cities set temperature records in 1936 and were affected by the Dust Bowl just as they were on the Plains.

Minneapolis had its 100 hottest days on record in 1936, with nine. Detroit and Indianapolis also set records for extreme temperatures of 100 degrees in 1936, with eight and 12 degrees, respectively. The last time the temperature in Detroit or Indianapolis reached 100 degrees was in July 2012, while Minneapolis recorded a high of 101 degrees on June 20, 2022.

Averages are based on climate data for the period 1991-2020.

Temperatures could rise in the south as well. Although the South certainly faces hot conditions every summer, temperatures reaching 100 degrees are not as common as one might think.

The area lies at a latitude suitable for triple-digit temperatures, but high dew points and humidity levels, as well as its proximity to the Gulf of Mexico and the Atlantic Ocean, prevent high temperature readings.

Occasionally, a hot, dry air mass develops across the region and allows the mercury to rise across the south. Areas away from water usually have a better chance of seeing triple-digit temperatures.

Nashville had 20 days of highs of 100 degrees in 1954. The highest temperature recorded there is 109 degrees, recorded on June 29, 2012. The next day, Atlanta recorded its highest temperature – 106 degrees. Nashville reached the 100-degree mark last year for the first time since then. The last time Atlanta reached at least 100 degrees was in August 2019.

Closer to the Gulf of Mexico, New Orleans and Mobile saw well under 100 days. The most ever recorded in a single year for New Orleans is five in 1980 and eight in 2000 for Mobile.

Florida is typically thought of as hot and humid, but constant humidity plays a big role in keeping the thermometer from rising.

Tampa has never recorded a high of 100 degrees in records dating back to 1890. The mercury has only risen to 100 degrees once in Miami, on July 21, 1942. Off both coasts, Orlando has reached the high 100s several times, including Most recently on June 19, 2015.

Although the thermometer may not read 100 degrees often, the combination of heat and humidity can make it feel like 100 degrees or higher based on the heat index.

(More: What is the heat index?)

The Northeast typically escapes triple-digit heat. The lack of triple-digit temperatures in the Northeast is due to the region’s higher latitudes and a general lack of dry air.

However, the right setup sometimes forms with a strong area of ​​high pressure over the area that allows temperatures to rise above 100 degrees.

Triple-digit heat is a little more common near the mid-Atlantic. The last time the temperature in Baltimore reached 100 degrees was in July 2020, while the last time it reached in August 2016 for Washington, DC. New York City last reached 100 degrees in July 2012, while Boston reached 100 degrees on July 24, 2022.

Portland, Maine, and Burlington, Vermont, also achieved triple-digit marks; The highest temperature on record was 103 degrees in Portland and 101 degrees in Burlington.

Some cities in the region did not record temperatures reaching 100 degrees, including Buffalo, New York, and Caribou, Maine.

(More: Thermal safety)

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment, and the importance of science in our lives. This story does not necessarily represent the position of our parent company, IBM.

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