Bird’s Eye: It has been an intense spring, with unseasonable in every flavour you could ask not to have. Why? No one knows for sure, but scientists have their theories. And we have the pictures.

* Strange Spring: Explaining This Year’s Wild Weather Discovery News

Even though May is right around the corner, recent weather reports have been far from spring-like.

Snow fell this week on Minneapolis and Green Bay. Record-setting cold has settled on Seattle. And historic wildfires are burning in Oklahoma and Texas, where temperatures in the 90s are threatening to topple heat records. Meanwhile, 272 tornadoes swept the nation in the first half of this month – already breaking the all-time twister-count for April.

So, what’s up with the weather?

According to experts, this season’s higher-than-normal highs, lower-than-normal lows and extreme storms are, to some degree, symptoms of what tends to be a volatile time of year. But there are also some more insidious factors behind the latest round of weather grief, including an unusually strong La Niña, a strange pocket of warm air in Arctic, and overall climate warming.

* Texas’ Wildfires Alan Taylor – In Focus

* Tornadoes Sweep Across the South Alan Taylor In Focus