Severe Weather in June

United States Tornado Averages (Source: NOAA)

June is one of the most active severe weather months of the year in the United States.  June has the second highest average annual number of tornadoes (243), according to NOAA.  In addition to tornadoes, a thunderstorm is “severe” if it has hail 1” in diameter or greater, or wind gusts of at least 58 mph.  The DC Metro Area has had significant severe weather outbreaks in the last 15 years.

2016: An outbreak occurred on June 21, with multiple reports of large hail and damaging wind gusts.  Since anemometers (used to measure wind speed and direction) are relatively uncommon among the general public, reports of wind damage are often noted in severe reports absent wind speeds.  The concentration of the 193 “severe” wind reports on this day were in the DC Metro Area.  An EF-0 tornado also occurred in Howard County, Maryland.

2013: Two significant severe weather outbreaks occurred just days apart in the Mid-Atlantic Region.  Four tornadoes hit Maryland on June 10, while another six confirmed tornadoes occurred in the DC Metro Area on June 13.  One of the June 13 tornadoes was an EF-0 in Montgomery County, Maryland.  It was on the ground for more than 20 minutes, with a 21 mile track from North Potomac to Burtonsville.

2012: While June 2012 is often remembered for the highly destructive June 29 “derecho,” the DC Metro Area saw two other significant outbreaks earlier that month.  One occurred on June 1 with 38 tornadoes concentrated in the Mid-Atlantic Region.  Of these, Maryland had a state record of 10 tornadoes, which remains the highest state-wide single day total.  The strongest was an EF-1 in Harford County, with peak wind speeds of 86-110 mph. 

A few weeks later on June 22, the primary type of severe weather was damaging winds.  Two downbursts occurred in Maryland, one each in the towns of Bladensburg and Johnsville.  A downburst is an area of strong winds that occurs when cold air located high in the thunderstorm accelerates as it descends toward the ground.  These winds spread out as they reach the ground, where speeds can approach 100 mph.  That’s equivalent to the wind speeds in an EF-1 tornado.

2008: The severe weather on June 4 was one of the most widespread and destructive episodes in the DC Metro Area.  In the mid-afternoon a squall line passed through the DC Metro Area.  It produced a significant amount of damage, most notably widespread power outages that resulted from downed trees and power lines.  Four confirmed tornadoes also occurred, with one in Maryland and three in Virginia.