The probability of a tornado touchdown somewhere in the U.S. jumps to nearly 80 percent in May and nearly 90 percent in June.
The contiguous U.S. has warmed 2.1°F since the first Earth Day in 1970.
While this has been a snowy winter, the past 50 years have shown a trend of less overall spring snow cover in the Northern Hemisphere.
Spring is arriving earlier across the U.S. by an average of three days.
For the first time in 20 years, the U.S. is on track to set more record lows than record highs in 2013.
Foliage color and timing has been starting later, on average, in a warming world.
Record highs have outpaced record lows by a bigger margin each decade since the 1960s.
The highlights of NOAA's 2013 Spring climate summary.