January: This is "rain death from the sky" month. B-52s armed with nuclear weapons crashed in 1962 (Goldsboro, North Carolina), 1966 (Palomares, Spain), and 1968 (Thule, Greenland). After the third crash, the Air Force finally figured out that it's a terrible idea to keep nuclear armed bombers in the air at all times. Hey, once is an accident and twice is a coincidence, but three times? That's a trend! For good measure, in 1978, a Soviet military satellite probably powered by a significant quantity of highly enriched uranium, Cosmos 954, fell back to Earth, spreading the good stuff across Canada. When it rains, it pours ... fissile material.
Still, my pick has got to be the 1995 Norwegian rocket incident. In January 1995, the Russians mistook a Norwegian sounding rocket for a U.S. missile launch. Boris Yeltsin later claimed he had activated the Russian "football" that would allow him to order a nuclear retaliation. It's hard to figure out how dangerous the moment was, but I like the idea of a possibly inebriated Yeltsin staring at the Russian football and yelling, "All the blinking lights! My head is killing me!" Really, anytime you can hang the fate of the world on the decision-making of Boris Yeltsin after a couple of stiff ones, I say go for it.
February: So, we've lost more than a few nuclear weapons, but usually in the deep sea. But after a 1958 mid-air collision, we lost on in the shallow waters around Tybee Island, near Savannah, Georgia. The Tybee bomb is the gift that keeps on giving, with periodic efforts to find the nuclear weapon. The most recent search was in 2004. After detectors found a small amount of radioactivity, teams searched for 90 days. An Air Force official "said even if the 7,600-pound bomb were found, it is probably best left where it is -- entombed in an estimated 15 feet of muck." Way to get after it, boys.
March: I have high standards for aircraft-related mishaps, but the 1958 incident at Mars Bluff is a doozy. (What's with 1958, huh?) The B-47 crew had failed to secure the bomb in the bay and, while attempting to replace a "locking pin" in flight, accidentally tripped the bomb release. The bomb landed in a residential area in the unincorporated hamlet of Mars Bluff near Myrtle Beach, South Carolina -- and exploded. Fortunately, only the high explosives detonated. But the impact crater can still be seen today. "Not too many people can say they've had a nuclear bomb dropped on them," Walter Gregg, the man who lost his house to the accident, told a local newspaper. "Not too many would want to." Gee, you think?
A runner up is the Soviet submarine K-129, which sank in March 1968 with all hands aboard and a number of nuclear weapons. The United States contracted with Howard Hughes to build the Glomar Explorer deep-sea drill ship to clandestinely retrieve much of the wreckage from the ocean floor. But this doesn't win, as we've got another sunken Soviet submarine coming up later.