A severe weather outbreak shifted into gear starting May 16, with over 235 reports of severe weather, primarily in Nebraska, northern Kansas and far northern Missouri. This included three weak (EF0 or EF1) tornadoes in Linn and Livingston Counties, Missouri, according to NWS damage surveys.

Of the 130 damaging wind reports, 11 of them had reports of winds gusting over 74 mph. The highest was a gust of 90 mph in Concordia, Kansas.

There were 95 hail reports, with nearly 30 being hail greater than 2 inches in diameter. Baseball sized hail was reported in Kansas and Nebraska.

On May 17, there were another 280 reports of severe weather, mainly across South Dakota and southern Minnesota to eastern Nebraska, western Iowa and northern Kansas. At this point, there have been 20 confirmed tornadoes on this day.

The most damaging of these struck areas in Howard County, Nebraska, near St. Libory, about 10 miles north of Grand Island, around 5 p.m. CDT.

The NWS rated this an EF3 tornado with peak estimated winds of 160 mph. Four homes were destroyed, but nobody was injured, as residents took shelter after receiving the NWS tornado warnings.

Another damaging tornado which prompted a rare tornado emergency from the National Weather Service appeared to track near or over parts of Hebron, Nebraska, near the Kansas state line about 65 miles southwest of Lincoln. The NWS rated this tornado EF1.

Damage was also reported from a radar-confirmed tornado north of Ashland, Nebraska, between Lincoln and Omaha. Homes near Plattsmouth, Nebraska, south of Omaha near the Missouri River, were also reported damaged by an apparent tornado.

Tornadoes were also reported in parts of northwest Iowa and southern Minnesota May 17, including near Mason City and Worthington.

Thunderstorm wind gusts up to 82 mph were clocked near Estherville, Iowa. A grain elevator was damaged in Greenville, Iowa, by strong thunderstorm winds. There were 156 wind reports on May 17, with 9 reports having gusts over 74 mph.

Palmer, Nebraska, saw a hail report of 3.5 inches in diameter, just one of the 88 hail reports that day.

For our walkthrough of the events as the storms unfolded, below is our live blog from May 17.

(MORE: May 17 Outbreak)

May 18 Severe Weather

There were over 300 reports of severe weather on May 18, primarily from the Great Lakes and Midwest to the Central Plains, including 15 tornadoes confirmed so far.

Most of the tornadoes this day were in a small area of northeastern Kansas, southeastern Nebraska, far southwestern Iowa and later, just northeast of Kansas City.

Multiple storm chasers witnessed tornadoes in Washington and Marshall Counties, Kansas, near Blue Rapids. Damage was reported to grain bins northwest of Frankfort, Kansas.

Multi-vortex tornadoes were also seen in parts of extreme southeast Nebraska near Pawnee City and Falls City. KETV-TV reported tree damage in Auburn, about 60 miles south of Omaha. The NWS in Omaha has reported at least 2 EF1 tornadoes so far. Kansas City also has one EF1 reported so far, and we have an EF1 tornado that was reported in Morris and Lyon County, Kansas. This number could increase as more surveying is done. At this point, there are 25 tornado reports.

There were also numerous reports of thunderstorm wind damage from a cluster of severe thunderstorms that rolled through Illinois, Indiana and Lower Michigan.

Tree branches were broken in parts of Chicagoland where wind gusts up 79 mph were clocked at Midway Airport. There were 262 wind reports, with the highest being a gust of 92 in Jarbalo, Kansas.

In Indiana, some barns and outbuildings were damaged by the strong wind gusts.

And in Michigan, three planes were flipped at Lansing's Capital Airport where gusts to 68 mph were clocked. Roof damage was reported in Woodland and in the north Detroit metro suburb of Rochester Hills.

There were also 69 hail reports, with the highest being a report of 2.75 inches in Sheridan, Missouri.

For more information as the storms unfolded, check our live blog that was ongoing during the storms.

(MORE: May 18 Oubreak)

May 19

The May 19 severe threat was severely diminished but is still worth mentioning. While there was only one tornado touchdown in central Texas, there were 156 wind reports along the cold front's path across the East. The main areas of wind reports were across the Southern Plains, the parts of Ohio, Indiana and Michigan as well as and parts of New England. The highest was a gust of 76 mph in Wayne County, Michigan.

There were also 15 hail reports.

Over 1,000 storm reports occurred between May 16 - May 19, with at least 42 tornadoes confirmed so far.

Quieter May, Until This

On average, May is the month with the most tornadoes in the U.S., as the graph below shows.

But that wasn't the case prior to this outbreak.

Check out how relatively blank the map below was of both reports of tornadoes and confirmed tornadoes through the first two weeks of the month.

Only a rash of eight confirmed tornadoes from supercell thunderstorms on May 6 in southern Mississippi stands out.

That's because the weather pattern in early May was generally cooler than average in the eastern and central U.S. but hotter than average in the West. It's exactly the opposite pattern you typically need for more widespread severe weather later in spring east of the Rockies.

Rob Shackelford is a meteorologist and climate scientist at weather.com. He received his undergraduate and master’s degrees from the University of Georgia studying meteorology and experimenting with alternative hurricane forecasting tools.