According to the U.S. Department of Agriculture, raw meat should not be cooked and consumed if it is left out and unrefrigerated for more than two hours. In temperatures above 90 degrees Fahrenheit, the meat should not be consumed if it is left out for more than an hour.
The USDA recommendations are based on the rates at which bacteria multiply. Bacteria begin forming on food almost immediately and double every 20 minutes in temperatures above 40 F. This is known as the "danger zone" for meat. The USDA also cautions that the toxins that may result from raw meat left unrefrigerated for too long are resistant to heat, so cooking the meat does not kill the bacteria.