Believe it or not the earliest significant snowfall (that's a snowfall of 2 or more inches) in the state of South Dakota occurred on September 1st. While it was officially still summer, Deerfield, in the Black Hills, received four inches of snow on September 1st, 1970.
On September 1st and 2nd, 1990 severe thunderstorms tore across portions of northwest South Dakota. The thunderstorms produced huge hail and ferocious winds. Hail as big as grapefruit fell in Sorum (in Perkins county) doing tremendous damage to houses and farm buildings. On the 2nd, thunderstorm winds approaching 90 miles an hour ripped the roofs of outbuildings and in some cases carried the debris for over 2 miles.
It is often joked about that mobile homes attract tornadoes. This, of course, is not true, but it seems that mobile homes are always the hardest hit by tornadoes. The misconception comes from the fact that there are large numbers of mobile homes in many of the most tornado prone regions of the country. The fact that these are among the most wind-vulnerable of all homes, and therefore even the weakest tornado will likely cause extensive severe damage, doesn't help matters any.
The earliest freeze on record in Sioux Falls occurred on September 3rd, 1974 when the morning low dipped to 31 degrees. Needless to say a little frost in early September is not recommended if you want to keep your plants alive although it's nothing compared to a hard freeze.
On September 4th, 1913 the temperature hit a scorching 104 degrees. That's the hottest temperature recorded in the month of September in Sioux Falls. What's unusual is that September 5th and 6th of the same year also hit 104 degrees. The record of 104 degrees has been equaled twice since...in 1922 and 1976...both on September 6th.
One of the many forms of lightning is called sheet lightning. Sheet lightning occurs when either the lightning flash occurs inside of a cloud or intervening clouds obscure the flash such that a portion of the cloud (or clouds) appear as a luminous white or blue sheet.
On September 6th, 1984 thunderstorms produced damaging high winds in and around the Black Hills. Winds gusted to an estimated 100 miles an hour at Mt. Coolidge (in Custer county) and to 75 miles an hour over the northern Black Hills and adjoining Plains. The winds damaged many trees, in some cases snapping branches as big as six inches in diameter. Winds also caused power outages in many areas and damaged numerous roofs, buildings, and signs. In the Martin area (Bennett county) winds estimated at 90 miles an hour destroyed several small buildings.
The days thunderstorms spawned nearly 20 range fires in the southwest and south central which burned thousands of acres of rangeland.
On September 7th, 1971 around the evening rush hour Sioux Falls was hit by a severe thunderstorm packing high winds. Winds estimated between 70 and 90 miles an hour caused extensive damage on the southwest side of town. The Park Ridge shopping mall was hit hard by the storm and considerable damage was also done at Western Mall. Damage was mostly to roofs, windows, as well as trees and utility lines. Four people were injured by broken glass at the Western Mall when a skylight was broke by the storm. Total damage was estimated at $60,000.
A strong cold front raced across South Dakota and into Iowa and Minnesota on September 8th, 1977. The front brought tremendous winds across the state and into western sections of Iowa and Minnesota. At Rapid City winds gusted to 75 miles an hour at the airport. The strong winds leveled many trees and damaged buildings, roofs, and broke windows. Portions of western South Dakota reported blowing dust which greatly reduced visibilities and led to many traffic accidents.
However, the high winds were even more widespread in the east. About 12 miles south of Ft. Pierre 68 mile an hour winds ripped a camper off of a truck and demolished it. 70 mile an hour winds destroyed a two and one-half million gallon oil tank near Watertown.
On September 9th and 10th, 1983 strong winds blasted through east central South Dakota, leaving in it's wake damaged crops, hundreds of downed trees, broken windows, damaged roofs and buildings, downed power poles, and damaged vehicles. Gusts of up to 75 miles an hour in Huron moved a semi trailer one-half block into a truck. The winds also tore a roof off of a building and into a propane tank. The propane tank was ruptured resulting in the loss of 4,000 gallons of propane. Standing crops of corn, beans, and sunflowers suffered extensive damage in many areas with losses up to 50% reported.
Gusts of 90 miles an hour hammered Lake Poinsett. Numerous roofs were ripped from area buildings and extensive damage was done to boats, docks, and nearby cars at Lake Poinsett. At Lake Preston (in Kingsbury county) a 1,000 gallon tank was torn loose and blown a mile from it's original resting spot.
During the drought year of 1988 even on the seemingly rare days when thunderstorms did develop they didn't help any. On September 10th, 1988 thunderstorms developed across south central sections of South Dakota bringing too little rain, too late in the year to help much. To add insult to injury lightning started numerous fires in the parched range lands. The fires burned nearly 14,000 acres of grassland and some 4,000 acres of timber. The resulting damages exceeded $60,000.
1992 was a record year for tornadoes across the United States. In 1992, 1,293 tornadoes were reported across the country. A normal year would have 700-800. The month of June 1992 had 399 reported touchdowns which is the record for a single month.
Sioux Falls had to deal with the hazards of fire and water on the same night back in 1984. Late in the evening of September 12th and into the morning of the 13th, 1984, thunderstorms rolled through the area producing dangerous lightning and heavy rains. The frequent lightning strikes around the city started eleven separate fires. One fire just east of Sioux Falls took 30 volunteers to extinguish. However, most of the fires did only minor damage.
To make matters worse the thunderstorms dumped around 1 inch of rain in an hour (.91 of an inch at the airport) causing local street flooding. In some areas the water was over one foot deep across the roads.
During the September of 1986 the Sioux Falls airport received 9.26 inches of rain. That is the wettest September and the third wettest month for any time of year on record for Sioux Falls. Most of the rain fell between the 10th and the 21st. During this eleven day period flooding occurred on the Vermillion, lower James, and Big Sioux Rivers and their tributaries. Several home were flooded in Flandreau while many rural roads were closed across the area.
An unseasonably early freeze hit portions of western South Dakota on September 14th, 1993 while an early frost struck the east on the 15th. On the morning of September 14th, 1993 some low temperatures included 24 degrees at Rapid City, 19 degrees at Camp Crook (in Harding county) and Porcupine (in Shannon county), and 31 degrees at Pierre. The 24 degree low at Rapid City shattered the old record by an impressive 10 degrees and was the earliest in the season that a temperature below 25 degrees has ever been recorded. By the time the air mass reached eastern South Dakota, and western Minnesota, and Iowa on the 15th the temperatures had moderated a bit. Still temperatures at or below freezing were common bringing an early frost to the area.
Sioux Falls residents received a rude awakening on the morning of September 15th, 1977 as thunderstorms rolled through the city. Over two and one-half inches of rain fell in the city in an hour and 15 minutes. The large amount of rain in a short period of time led to street flooding in some areas. Lightning strikes from the storms also started several small fires.
Larger hailstones, obviously, can do much more damage than small hailstones. Not only do larger stones have more weight, but they fall at much faster speeds. A pea-size stone falls at around 22 miles an hour while golf ball size hailstone falls a around 60 miles an hour. By the time the hailstones are the size of baseball's they fall at a frightening 100 miles an hour.
If you've ever heard the weather saying "where lightning strikes, one can dig a well" you'll be glad to know that there is a little truth to the old folklore. Lightning will frequently strike where there is an underground spring or even standing water.
On September 18th, 1988 hail the size of hen eggs blew out numerous windows and did tremendous damage roofs all over the town of Platte (in Charles Mix county). Crops within a 12 mile radius were largely destroyed. Damage to area buildings totaled $5 million dollars and crop damage approached $750,000.
Could you imagine receiving a little snow today? Well, it happened in Sioux Falls on September 18th, 1929 when the city recorded a trace of the white stuff. That's the earliest in the season that snow has been reported in Sioux Falls.
The latest occurrence of a 100 degree temperature on record in Sioux Falls occurred on September 19th, way back in 1895. The temperature hit 100 degrees on the nose that day and is now one of the older records still standing for the city.
Most of us think of May through August when we think of big thunderstorms, but September has its moments too. In fact the largest hailstone known to have fallen in the United States fell in Coffeyville, Kansas on September 3rd, 1970. The amazing stone weighed over one pound and was 44 centimeters in circumference.
Sioux Falls averages around 25 days a year with high temperatures above 90 degrees and 2 days above 100 degrees. The most 100 degree days on record for one year occurred during the summer of 1936 when the mercury equalled or topped 100 degrees 21 times. That's about two decades worth of 100 degree days in one summer. The second most occurred in 1988 with 14 days.
Portions of Death Valley in California average 140 to 160 days over 100 degrees every year. Sioux Falls only hit 100 degrees 203 times between the years of 1893 and 1988.
The danger of sunburn is obvious when the sun is shining directly on you. But clouds, a beach umbrella, or water don't offer as much protection from the sun's harmful UV rays that cause sunburn and increase the risk of skin cancer as you might think. About 40% as much UV reaches shaded areas as in sunny areas. Thin clouds, on the other hand, allow up to 80% of the UV rays through. UV rays still maintain 80% of their strength even after penetrating one and one-half feet under water and maintain 70% to three feet under water. Obviously, sunblock or not going outside at all is the best protection.
Although summer had just ended portions of South Dakota were going straight into winter back on September 23, 1984. An early season snowstorm brought more than a foot of snow to some locations in the northwest. This is late September and portions of the lower elevations were already picking large amounts of snow! Amounts of six to 12 inches were common over Harding and Perkins counties as well as portions of Meade and Butte counties. Roads in these areas were covered with snow and slush and became icy. Fortunately, the ground was still warm from the summer's heat so the snow melted from beneath keeping the roads passable. The remainder of the western third of the state generally only had light snow.
Tornadoes and Hurricanes get all the press for their destructive powers, but floods actually carry a higher death toll. Floods are the United States biggest weather killer... over 100 people a year die in floods. Around 60% of flood victims are caught in their cars and most of those perish while trying to drive through water that is flowing across the road.
In both human and economic terms the Great Flood of 1993 was the most devastating in modern U.S. history. It was a catastrophe across portions of 9 states with losses estimated up to $20 billion dollars. Some amazing numbers linger from the floods. Over 50,000 homes were damaged or destroyed forcing the evacuation of some 54,000 people. In all the floods took 50 lives. Water level records were set at 49 places on the Missouri River system and at 43 places on the upper Mississippi River system. The flood was notable for its duration as well as its size. Flooding began in March with record floods beginning in May and continued into September.
Lightning is a major weather killer across the United States. In an average year around 60 lightning deaths are reported. More deaths than this are probably caused by lightning, but are not officially recorded as such (possibly recorded as cardiac arrest etc.).
Between 1959 and 1990 eighteen lightning deaths were reported in South Dakota alone. The people most susceptible to a lightning strike are golfers, boaters, and people hiking in higher elevations.
Here's another one of those early season snowstorms in South Dakota. On September 27th and 28th, 1985 residents of south central South Dakota received an early taste of winter as up to 18 inches of snow piled up in the Winner area (in Tripp county). Most areas received 3 to 6 inches. Some snow amounts included 5 inches at Martin (Bennett county)...6 inches in Winner...and 10 inches around Burke (in Gregory county). The storm didn't cause very many travel problems, but greatly hampered the harvesting of the summer crops.
On September 28th, 1985 as south central South Dakota was in the midst of an early season snowstorm Sioux Falls picked up a measly nine-tenths of an inch of snow. This amount is significant, however, as it is the earliest measurable snow on record for Sioux Falls. The total of nine-tenths of an inch also makes it the snowiest September on record.
This snow tied the date of the earliest measurable snowfall on record which was originally set in 1945 when one-tenth of an inch fell.
On September 29th, 1899 the morning low temperature fell all the way to 13 degrees. That's the coldest temperature ever recorded in the month of September in Sioux Falls.
Floods kill more people in an average year than do tornadoes or hurricanes. Of the over 100 people that die on average 60% of those are in their cars. Flowing water and moving cars don't mix. Water typically moves at 6 to 12 miles an hour in a flood.
As we all know water is very heavy. The weight and speed of the flowing water give it more momentum than many think. For each foot the water rises it pushes on a car with another 500 pounds of force. More importantly, water is quite buoyant. Essentially, a car weighs 1500 pounds less for each foot of water flowing across a road. Water only two feet deep will carry away most cars.