It's really annoying when global warming deniers point to a city here or there that has really cold temperatures in the summer. We need to rebut with our own individual data points. Here's one:

Roughly 2,000 Nebraska cattle die in heat wave - A mature cattle nearing slaughter is worth around $1,000. I doubt those ranchers are going to be receptive to anybody who denies global warming. Furthermore:

Heat waves usually strike somewhere in Nebraska every two or three years, but last week's heat was unusual because of how soon it struck and how quickly cattle died

One thing you could call into the radio with is, "Haven't you noticed heatwaves are getting longer and hotter, and that winters are shrinking?" In other words, appeal to the opposition's trust of anecdotal evidence. The deniers don't care about statistics. If they did, they would have already been convinced.

For future reference, if a global warming denier spouts another single data point, simply do a Google News search for "heatwave" and you'll find plenty of rebuttals.