A persistent upper-air pattern that lapped into March created a nation of contrasts last month.

Often, what happens in the East is the mirror opposite of what goes on in the West, but we've never seen anything quite like this.

In the Northeast region, which includes Pennsylvania, New Jersey, and Delaware, the overall average temperature for the month was 12.1 Fahrenheit, or 10.4 degrees below the 20th Century average, according to the National Climatic Data Center.

That was the second-coldest February in records dating to 1895, and the average daytime highs for the month were the lowest for any February.

Meanwhile, the West, consisting of Washington, Oregon, Idaho, California and Nevada, set a record for the warmest February.

Getting back to the Northeast, Philadelphia's February average temperature officially was 25.8, or close to 10 degrees below normal, but as cold as it was, this region was in a relative banana belt.

The average temperature for all of Pennsylvania was 16.3; 22.3 in New Jersey. But the states that brought down the average included Maine, at 5 degrees, and Vermont, 5.3.

What was going on?

The SparkNotes: During February a pattern took hold with higher atmospheric pressures in the West, which favor dryness and warmth, and lower in the East, favoring cold and storminess.

Only journalistic integrity prevents us from saying that the pattern has flipped for good.