[givemELL]

Of course, the jet stream does not itself produce the cold weather, it is only a contributor to its distribution.

[HiTech RedNeck]

Too — temperatures measured at ground level alone are misleading. The atmosphere has a considerable vertical dimension. If the surface is getting warmer but the upper air is getting colder, the net thermal energy difference might be zero or negative.

[patriciaruth]

You notice how they never venture into wondering WHY the jet stream deviated.