Warm is not synonymous with high in this case; I wouldn't call 40 degrees warm.
Temperature is such a relative word... since ice will melt at 40 degrees, it is possible to say that the temperature is warmer! In Arizona, when the summer temperatures dip below 100 degrees, our TV weathermen love to say 'we can expect cooler temperatures over the next few days'! Oh, goodie!!!
Let's hope that this winter is warmer than last year!