There are also things you can do to assist.
And there are also some things you shouldn't do.
"You can't look at tragedy and not want to help the community," Chicago Mayor Rahm Emanuel said Tuesday.
The Red Cross is mobilizing one of its Chicago volunteers. She'll fly to the disaster zone Wednesday. The mental health volunteer has been on 10 different disaster deployments.
Karen Hoganson specializes in mental health counseling for victims and first responders. She leaves in the morning for Oklahoma City and she's ready to do whatever is needed.
"When this first happens, they need direction. They need to eat and drink. First aid is important," said Hoganson.
Hoganson has travelled to major disasters many times over the last 11 years. She says they're all different, but the needs of those who have lived through them are similar.
Many residents who survived the powerful storm uninjured still lost everything. They need help with the basics to get them through the first few days.Chicago Red Cross urges donations At the Greater Chicago headquarters of the Red Cross, they are encouraging people to donate money.
"We want to make sure that people have what they need, when they need it," said Red Cross chief communications officer Martha Carlos. "We're still determining what that is. We know in large disasters like this the immediate needs are about foods, they're about shelter. They're things like replacement medication and diapers and infant formula."
If you want your cash to go directly to supporting the Oklahoma tornado disaster, you should specifically note that in your donation. What you shouldn't do is send specific items, clothing or shoes.
Don't drive down to help on your own.
"We don't want to tax an overburdened system right now," said Carlos. "So you don't want to just get in your car to go down there to help, even with the best intentions."
How to give:
People who wish to make a donation to support the Red Cross response to the disaster in Oklahoma can visit redcross.org, dial 1-800-REDCROSS or text REDCROSS to 90999 to make a $10 donation.
You can also help the Salvation Army's efforts by giving online at SalvationArmyUSA.org or texting STORM to 80888 to make a $10 donation.Be prepared for disaster And, what if a tornado strikes the Chicago area? Carlos says you and your family need to seek shelter in the lowest spot without windows, but you also need a specific room and plan.
Many residents who survived the powerful storm are uninjured but still lost everything. They need help with the basics to get them through the first few days.
That's why the National Safety Council recommends putting together emergency kits that contain some of those things.
In the event of no power or if you are trapped, they recommend packing non-perishable foods that require no cooking, water, flashlights, basic tools, and even playing cards to help keep you occupied while you wait for power or to be rescued.
They suggest enough to last three days and you should keep it in the basement or wherever you are most likely to seek shelter.
The Red Cross also has a free tornado app which warns users of severe weather and has a function to let loved ones know you're OK after a twister or storm.
Like the Red Cross, some golden retrievers from the Chicago area are headed to Oklahoma to do their part. They are comfort dogs from Lutheran Church Charities and they were invited by an Oklahoma church.
The charity has several dogs that are rotated between locations. They have traveled a lot lately, to New York for Superstorm Sandy, to Newtown, Connecticut, and most recently to Boston and Waco, Texas.
"They help people process what's happened to them," said Lutheran Church Charities' Tim Hetzner.
Kevin Durant, a three-time scoring champion for the NBA's Oklahoma City Thunder, posted on his Twitter account that he was praying for everyone involved. He added: "Everybody stay safe!" Durant donated $1 million to the American Red Cross for disaster relief.
Los Angeles Dodgers star outfielder Matt Kemp, who is from Oklahoma, posted Monday on Twitter: "I'm giving $1000 for tonight's HR and every HR until the All-Star break for the victims of my hometown in OKC. #PrayforOklahoma"
The Associated Press contributed to this report.