Many people that live in the mid-west are familiar with sudden changes in air temperature. They are usually associated with a passing cold front or the cool down-burst of a thunderstorm. However, on rare occasions, the air temperature can rapidly increase due to a phenomenon called a heat burst. Within a matter of minutes the wind speeds can exceed 65 mph and the air temperature can increase by 20°F or more. As strange as that sounds, they are well documented (see bottom of article). Even more intriguing, these events almost always occur late at night or in the very early morning hours.
If order for this strange event to occur, all the right ingredients must get mixed together at just the right time. First, rain from a decaying thunderstorm must fall through a layer of very dry air, which by itself is uncommon. Second, as the rain falls through the drier air, it must evaporate and cool rapidly. This creates a localized blob of very dense cool air that is much heavier than its surroundings. Because the air is heavier than its surroundings, it rapidly descends through the atmosphere towards the ground below. Third, as the blob of cold air descends, it warms due to compression. However, it must have sufficient downward momentum that it overshoots the atmospheric equilibrium (warm air rises, hot air rises even faster). When the air hits the ground, it spreads out like a pancake. Those in the area will experience strong winds and a rapid increase in temperature.
The affects of a Heat Burst can last up to an hour until the atmosphere equalizes or the heat dissipates. Because the air descends rapidly, strong winds usually accompany the heat burst. It’s not uncommon for wind speeds to exceed 60 mph or more, similar to a micro-burst, which can tear shingles from rooftops and knock down trees.
One of the more recent heat bursts occurred in Wichita, Kansas in the middle of June 2011 just after midnight. Just how warm can one of these Heat Bursts get? Very warm. In some cases it can get downright hot, whereby temperatures can easily exceed 100°F in the middle of the night. It can also happen in a matter of minutes.
Even though heat bursts are rare, the United States will typically see about one a year during the warm summer months. Below are some of the more notable heat burst events that have occurred in the United States:
- Grand Island, Nebraska, 11 June 2013: Temperature jumped from 74.2°F (23.4°C) to 93.7°F (34.3°C) in the 15 minutes between 2:57 and 3:12 AM.
- Wichita, Kansas, 9 June 2011: Temperatures rose from 85 to 102°F (29°C to 39°C) between 12:22 and 12:42 am. The heat burst caused some wind damage (40–50 mph or 64–80 km/h).
- Sioux Falls, South Dakota, 3 August 2008: Temperatures rose rapidly from the lower 70°F to 101°F (21 to 38°C) in a matter of minutes. Wind speeds also rose with gusts up to 50–60 mph (80–97 km/h).
- Cozad, Nebraska, June 26, 2008: Wind gusts reached 75 miles per hour, as the temperature rose 20°F (11°C) in a matter of minutes.
- Midland, Texas, June 16, 2008: At 11:25 pm a wind gust of 62 mph occurred as the temperature rose from 71°F to 97°F in just a few minutes.
- Emporia, Kansas, 25 May 2008: Reported temperature jumped from 71°F to 91°F between 4:44 am and 5:11 am (CDT) as the result of wind activity from a slow moving thunderstorm about 40 miles to the southwest.
- Oklahoma, May 22–May 23, 1996: The temperature in the towns of Chickasha rose from 87.6°F to 101.9°F in just 25 minutes, while the temperature at Ninnekah rose from 87.9°F to 101.4°F in 40 minutes. In addition, wind damage was reported as winds gusted to 95 mph in Lawton, 67 mph in Ninnekah, and 63 mph in Chickasha.
- Kopperl, Texas, 1960: Nicknamed “Satan’s Storm” a heat burst caused by a nearby decaying thunderstorm sent the air temperature rocketing to 140°F! The event destroyed crops and other vegetation due to rapid dehydration.
- Cherokee, Oklahoma, 11 July 1909: at 3:00 am in the morning, a heat burst south of Cherokee, Oklahoma reportedly caused the temperature to rise briefly to 136°F, desiccating crops in the area.