The weather observations record from the NWS for Hutchinson Municipal Airport, KS. At 10:52PM, the station recorded a sudden 53 MPH wind gust and 12 degree rise in temperatures from the previous hour's observation.
The National Weather Service office in Wichita reported on its Facebook page that a "heat burst" occurred in Hutchinson, KS during a thunderstorm around 11 o'clock at night. The temperature in Hutchinson went from 73°F at 9:52PM all the way up to 87°F at the heat burst's highest intensity. This led to some confusion over what exactly happened, and my Facebook feed exploded with everything from "Yet another product of global warming" to "We're in the end times!111!!"
While fun to think about, neither of those are right (the first one definitely not, the second one I hope not). Heat bursts are not fully understood by meteorologists, so there are a few theories out there to explain their existence. The way I understand it is that a heat burst occurs when an elevated thunderstorm (with bases a few thousand feed above ground level) collapses into dry air below it -- the storm can no longer support itself, and it literally collapses as a column of precipitation. As this heavy precipitation falls through the dry air below the storm, it quickly evaporates and cools the air around it. This cold, dry air (since it's denser than the surrounding air) sinks rapidly towards the surface, and quickly heats up due to compressional heating. Once this rapidly moving column of dry, hot air hits the surface, it can cause surface temperatures to warm up 10-30+ degrees Fahrenheit and create damaging wind gusts well in excess of 60 MPH in just a minute or two.
The other theory I've seen is that an area of cold, dry air enters the thunderstorm itself, evaporates the precipitation inside the storm, causes the air to cool even further, sink, warm, and hit the ground. Either way, the process is caused by rain that evaporates and causes air to become more dense than its surroundings, allowing it to descend (and therefore warm) quickly.
I've never experienced one, but if you're standing outside when it happens, I've heard it described as opening a hot oven in front of your face. The heat burst doesn't last long...depending on how hot the temperatures get, it usually mixes out and the air returns to its previous temperature after an hour or so.
A few hours after the Hutchinson KS heat burst, a smaller one occurred at the Coffeyville Municipal Airport along the OK/KS border in southeastern Kansas. Temperatures in Coffeyville jumped up from 68°F at 1:52AM to a maximum of 81°F about an hour later.
For the weather geeks among us, I went and found a Skew-T from Lamont, OK taken at the unusual time of 1:00 this morning, which was just a few hours after the Hutchinson heat burst, and right around the time of the nearby Coffeyville KS heat burst. You can see that there is a huge area of dry air between the surface and about 500 millibars, with a small pocket of moisture available in a skinny area of CAPE in which elevated convection might be able to fire. This is in line with the heat bursts that were recorded in the area last night. As the elevated thunderstorms collapsed into the dry air below them, dried out and quickly sank to the surface. Click the sounding to enlarge it in a new window.
Heat bursts aren't particularly common (as they require precise atmospheric conditions to occur), but they do happen a dozen or two times a year. An extreme heat burst made news last summer in Wichita, KS after causing temperatures to jump from the low 80s around midnight on June 9, 2011 to over 100 degrees by 1:00 AM. The Wichita Midcontinent Airport in western Wichita recorded a maximum temperature of 102°F at 12:42AM; Jabara Airport in northeastern Wichita recorded a temp of 102°F at 1:18 AM; McConnell AFB in southeastern Wichita recorded a temp of 100°F at 1:12AM.
Heat bursts are most common in the Plains where elevated convection is most common, but at least in one instance we've recorded a heat burst that occurred on the Delmarva Peninsula, causing temperatures in Salisbury MD to rise 13 degrees to 87°F at 2:00AM on April 26, 2009.
They're generally nothing to worry about in terms of abnormality or frequency. Heat bursts have happened for as long as there's been convection (thunderstorms) on Earth. The proliferation of personal and professional weather stations, and the growth of meteorology websites, allows us to better measure, understand, and hear about this type of phenomenon when it occurs.
To clarify my statement on heat bursts and climate change which seems to have ruffled some feathers, there was a misunderstanding in what I meant. In my diary this afternoon I stated that there was no link between heat bursts and climate change. I was responding to the people who keep saying that the air physically warmed up due to global warming. Their assertions are not true. It warmed up due to physical compression as it sank.