Mild winters leading to rat explosion in NE While some people may see less snow and ice in the winter months as a positive side effect of climate change, rats do too. Cities in New England are experiencing an explosion in their rat populations as a result of recent mild winters, reports CBS affiliate WBZ in Boston. They're not alone, either. Last summer, Chicago experienced a 28-percent increase in rat population. "Winter conditions slow down their breeding," Salem, Mass., Health Agent Larry Ramdin told WBZ."We had an explosion of rats we normally wouldn't typically see in a New England winter." In Salem, they are increasing the budget to try to deal with the problem. In Boston, inspectors found more than 50 burrows at two Fenway sites in August and evidence the rats were migrating to other nearby areas, WBZ reports. With temperatures on the rise globally, the problem may not be getting better anytime soon.