The National Weather Service in Paducah has expanded its heat advisory to include the entire Ohio Valley region, and parts of 13 states.The advisory is still in effect through Thursday evening. Dangerous heat index values will continue to run between 100 to 108 degrees, with some locations reaching even higher values. Only small chances of rain are forecast later in the week. The cumulative effects of daily extreme temperatures and humidity can be especially dangerous for the very young, the elderly, or anyone who has conditions that are aggravated by heat. Attention must also be paid to pets and livestock exposed to the heat for extended periods. A break in the heat may be on the way for the weekend with highs in the upper 80s.