Video of mammatus clouds by Jason Asselin
Though they may be associated with severe thunderstorms, mammatus clouds, like the ones in this popular Youtube video, are not necessarily an indication of severe weather.
Mammatus clouds form when air sinks, unlike most clouds which form due to rising air. This results in the pouches of condensation that give these clouds their bumpy appearance.
The turbulent atmosphere that creates these "upside down" clouds can be conducive to thunderstorms. Generally, a severe thunderstorm is eminent if mammatus clouds form on the underside of a cumulonimbus cloud. If they form beneath an anvil cloud, however, they are typically not threatening.
Asselin said that the video was taken around 8 p.m. CDT on July 22, and AccuWeather.com Expert Senior Meterologist Paul Walker said that coincides with a cold front that moved through the area. The high for that day around Iron Mountain, Mich., was 85. The day was also marked with high humidity. When the cold front moved through, it pushed down from atop the warm air and created the pockets in the clouds.
There were some thunderstorms in the area, but the temperatures evaporated much of the precipitation, leaving no measurable rainfall.
Thumbnail image by Phyllis Carlson, courtesy of AccuWeather.com Astronomy on Facebook.
In a state plagued by drought, Golden State residents are advised to play it safe with fireworks this Fourth of July.
After a wet June, July will begin with the threat for gusty thunderstorms and flooding downpours centered on the middle Mississippi Valley.
Americans will be hoping for clear skies this Saturday, July 4, as they look to enjoy dazzling fireworks displays, in addition to other popular Fourth of July activities.
The mercury soared to a whopping 36.7 degrees Celsius on Wednesday at London Heathrow Airport, setting an all-time July record high for the United Kingdom.
The heat wave that started across Spain and Portugal will spread across much of Europe this week with some of the hottest conditions of the year.
July Fourth will be stormy from the central Plains to the mid-Atlantic, while clear skies are in store for much of the Midwest and New England.
Stampede Pass, WA (1979)
A total of 5.8 inches of snow at 3,800 feet. (5.8 inches is a new record snowfall for July; the old record was 5.4 inches.)
Raleigh, NC (1981)
First of six straight days with measurable rain. (A total of 4.60 inches fell over the six-day period.)
Baltimore, MD Airport (1988)
50 degrees -- July record low.