A report from the federal government says the Midwest is already feeling the effects of global warming.
The report, from the National Oceanographic and Atmospheric Administration, documents changes that have already taken place, and says the Midwest will see them intensify.
It says the region will get hotter, with shorter winters and more extreme weather events such as heavy rains alternating with drought conditions. Water levels in the Great Lakes are likely to fall.
More carbon dioxide in the air could help some crops, but that's likely to be offset by erratic weather and more insects surviving milder winters.
Jane Lubchenco, administrator for NOAA and one of the report's authors, says the findings should motivate people to face the challenge.
"This is science that will inform policy-making: it doesn't dictate any particular solution, but it says this is important, we need to act sooner rather than later, and it affects you and the things you care about," she said.
Lubchenco says too many people think climate change is in the future or will only affect far-away places.
"This report demonstrates, provides the concrete scientific information that says unequivocally that climate change is happening now, in our own backyards, and it affects the things people care about," she said.
The government issued the report partly to help state and local governments respond. The report comes as the House of Representatives debates a bill addressing climate change.