Frequently Asked Questions

For Indiana

What is the most days ever recorded when the temperature was over 90°F?
Back in 1983 there were 58 days in which the temperature was over 90°F.

What is the most ice that has ever accumulated at one time?
The most ice that has ever accumulated at once in Indiana was 2″ back in 1988.

What is the biggest flood ever recorded?
The biggest flood ever to hit Indiana was back in 1913 when flood waters were 37 feet above flood stage.

What is the average number of tornadoes to touchdown per year?
The average is 20 touchdowns per year.

How many tornadoes does there have to be for it to be called an outbreak?
If there is more than 6 tornado touchdowns in a 24 hour period then meteorologists call it an outbreak.

Why is it so windy in Indiana?
Indiana is usually on the path of weather systems and has a flat terrian, both of which cause the strong wind in Indiana.

Why do cities near South Bend typically receive so much more snowfall in winter than other places in Indiana?
South Bend and cities nearby are located in the vicinity of Lake Michigan . This proximity and geographic position relative to one of the Great Lakes directly impacts the total amount of winter snowfall they receive.

During winter northerly and northwesterly winds occur frequently in this region. As Lake Michigan is oriented primarily north to south, winter winds from Canada travel the entire length of this lake. Moisture is evaporated from the surface of unfrozen Lake Michigan into this southward moving air mass as it approaches Indiana .

As the moisture laden winds contact the colder land surface at the southern tip of Lake Michigan , this air mass quickly cools and loses its capacity to hold this quantity of moisture. After enough cooling has occurred, the excess moisture is released as snowfall. This usually occurs in Indiana counties bordering Lake Michigan and is especially common in and around the city of South Bend . This entire process is referred to by meteorologists and climatologists as the “lake effect”.

Over the course of a winter season the accumulated differences in snowfall between this region and those to the south in Indiana are remarkable, as much as a 40 to 50 inch difference in total snowfall.

In General

What was the biggest tornado ever recorded?
The biggest tornado ever recorded was in 1925 when a 1.5 mile wide twister crossed, Missouri, Illinois, and Indiana at 70 mph.

What is the difference between a watch and a warning?
A watch indicates that conditions are favorable for severe weather to develop. You should remain alert for changing weather conditions and be ready to move to a place of safety. A warning means that dangerous weather is occurring or imminent and that you should seek safety immediately!

What is the heat index?
The Heat Index, also known as the apparent temperature, is an accurate measure of how hot it really feels when relative humidity (RH) is added to the actual air temperature. The National Weather Service derived the Heat Index in an effort to alert the public to the dangers of exposure to extended periods of heat, especially when high humidity acts along with the high temperatures to reduce the body’s ability to cool itself.

What is the windchill?
The Wind Chill Temperature Index, sometimes also known as the equivalent temperature, is used to describe how cold people and animals feel when they experience heat loss caused by the combined effects of low temperature and wind.

What is the difference between snowfall and snow depth?
Snowfall is the amount of fresh snow that has fallen during the 24-hour measurement period, while the snow depth is the total amount of snow on the ground and includes both old and new snow. Snowfall is measured to the nearest 1/10th of an inch while snow depth is measured to the nearest inch.

What is a State Climatologist?
A State Climatologist (SC) is a person designated by the state and the National Climatic Data Center as the official in charge of monitoring climate in the state.  Originally, SCs were employees of the federal government, but beginning in 1971, funding was provided by individual states.  As a result, SCs are located in different departments in each state, and a few states do not fund one at all.  Because of their different funding agencies, each has a unique set of responsibilities, although many include some public service.  In Indiana, we monitor weather and climate, provide public service to individuals, research scientists, government agencies, and industries, and conduct climate-related research.

What is a Tornado Watch?
A Tornado Watch is issued by the Storm Prediction Center in Norman , Oklahoma to alert people anywhere in the United States when atmospheric conditions are favorable for tornado development in their local area.

What should I do in such case?
Pay close attention to the weather outside, listen to local media (radio or TV), listen for your community’s tornado warning siren, and be ready to seek shelter.

What is a Tornado Warning?
A Tornado Warning is issued when a tornado has actually been sighted or is indicated by Storm Prediction radar. The tornado is actually occurring and imminent danger exists for people in the warning area. A warning siren sounds.

What should I do in case of Tornado Warning?
Seek immediate tornado shelter. If you are at home, seek shelter in the basement, the ground floor, center of the house, or any interior room or closet. Stay away from outside walls, doors and glass windows. DO NOT seek shelter in mobile homes, and DO NOT stay in your car or vehicle. If you are outside, protect your head and lie flat in a ditch, ravine or culvert (but watch for flooding).

What is a severe thunderstorm watch?
A severe thunderstorm watch is issued by the National Weather Service when the weather conditions are favorable for the development of severe thunderstorms. It tells you when and where the event is likely to occur. According to the National Weather Service, a thunderstorm is severe if it produces hail 1 inch in diameter or larger, winds of 58 mph or stronger, or a tornado. Watch the sky and listen to radio or TV to know when warnings are issued.

What is a severe thunderstorm warning?
A severe thunderstorm warning is issued when a severe thunderstorm is occurring or has been sighted or detected by radar. It indicates an imminent danger over the warned area. Seek shelter immediately. If you are inside, avoid taking a shower or bath. Do not use the phone (unless there is an emergency). Stay away from household appliances. Turn off air conditioners and unplug electrical equipments to avoid damages due to power surges. If you are outside, avoid being in contact with metallic objects and stay away from water, tall trees, towers and telephone poles to avoid lightning strikes. You can find shelter under shorter trees, but do not lie down, and watch for flash flood. More detailed information about how to get prepared can be found at the National weather service website: http://www.nws.noaa.gov/om/brochures/ttl.pdf

How many gallons of water are required to cover an acre of land to a depth of one foot?
The amount of water required is 325, 851 gallons. This also defines an “acre-foot” of water, a term which is often used in irrigation scheduling.

What is meant by a “water year”?
A water year is a continuous 12-month interval between October 1 of a given year through September 30 of the following year. This term is used by hydrologists to compare the total amount of precipitation between years in closer harmony with the natural seasonal ground recharge and discharge cycles (due to precipitation and evaporation) than if based on the calendar year.

What is dewpoint temperature? How it is related to air temperature?
Dewpoint temperature is the temperature at which a parcel of air would be saturated (relative humidity = 100%). When dewpoint temperature is close to air temeprature, it means that there is higher moisture content in the atmosphere and damper air mass