Atmospheric Scientist here at Weather Underground, with serious nerd love for tropical cyclones and climate change. Twitter: @WunderAngela
By: Angela Fritz , 10:44 PM GMT on July 16, 2011
Extreme heat is building across the Central U.S., and it doesn't look like it will let up for the region until Thursday or Friday. Excessive heat warnings, heat advisories, and excessive heat watches blanket the central U.S. from Texas north to Minnesota.
Temperatures will top 100°F in some locations, and heat indices could surpass 115°F. Expect that overnight lows might not get below 80°F—values that are 15 to 20 degrees above normal for much of the Upper Midwest. The heat is expected to remain in place for most of the week, but will begin to shift eastward by Thursday or Friday.
A strong ridge of high pressure is in place across most of the U.S., allowing high temperatures to build. Combine that ridge with the prolonged, intense drought across the southern tier, and you have a recipe for an extreme July heat wave.
In the Upper Midwest, enough moisture will be present to make the heat unbearable. The "heat index" is often referred to as the "feels-like" temperature—how hot it feels to your skin. When temperatures soar, humidity can exacerbate the heat. The Midwest has had just enough rain in the past couple of weeks to make the air more humid than it is down south, which is why the heat index will be so high in this region. The air moisture is also caused by agriculture. We often see high humidity where lots of corn is grown, especially Iowa.
Forecasters and public health officials alike are asking people to take precautions over the next week. Drink more water than you usually would, especially if you exercise or work outdoors. Avoid alcohol. Stay inside in air-conditioned buildings, and check on family and neighbors. Don't run the air conditioning too cool as this could lead to widespread power outages if everyone does the same. The demand on power plants will already be exceptionally high.
• Dallas, Texas
• Amarillo, Texas
• Oklahoma City, Oklahoma
• Kansas City, Missouri
• St. Louis, Missouri
• Omaha, Nebraska
• Des Moines, Iowa
• Rapid City, South Dakota
• Minneapolis, Minnesota
• Fargo, North Dakota
You can find your own local forecast by entering your city or zip code in the search bar at the top of the page.
Current U.S. Heat Index
This colored contour map shows current heat index. Heat index is the apparent temperature considering both the temperature and relative humidity. The key below the image shows the corresponding heat index for each color.
Current U.S. Temperature
This colored contour map shows current temperatures. The key below the image shows the corresponding temperature value for each color.
Current U.S. Relative Humidity
This colored contour map shows current relative humidity. Relative humidity is the ratio of water vapor contained in the air to the maximum amount of water vapor that can be contained in the air at the current temperature. The key below the image shows the corresponding relative humidity for each color.
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