 The British, it is said, love to talk about the weather. Personally, I've always found that to be an exaggeration: Britain's weather, to be honest, is not very interesting, though it can be a useful conversational filler if other topics are exhausted, or too ticklish to embark upon.  No, it's here in america that people really talk about the weather. One reason is the national addiction to numbers: rainfall, snow amounts, temperatures, windspeeds and so on are paradise for statisticians. a bigger one, though, is that american weather mirrors america itself, larger than life and prone to the most violent changes and contradictory extremes. It truly is worth talking about, and never more so than now.  I am no expert. But whether the reason is global warming, El Ni?o, La Ni?a, the alignment of the constellation Sagittarius, or simply punishment meted out by a capricious deity, this spring of which we have not yet reached the midpoint is already one for the record books.  The focus of the action, as usual, is the central and southern midsection of the country, a vast swathe of mainly flat territory bounded by the Rockies in the west, the appalachian mountains in the east, and the Gulf of Mexico in the south, where cold air originating in the arctic collides with the moist, warm airstream from the Gulf. In this region anything can happen, and this year it has.  You will already have read about the tornados. One day, 27 april, alone produced the deadliest single crop since 1974, in which some 300 people died in alabama and five other southern states. It was once flippantly said that tornados were God's answer to trailer-parks. Not however the mile-wide monster that bore down on the university town of Tuscaloosa 11 days ago, reducing sturdy homes to rubble and laying waste entire neighbourhoods.  and yet worse may be ahead. Last month may have been the most severe april ever for tornados, with 300 separate ones registered, a figure eclipsing even 1974. But april is not even the most tornado-prone month. More usually occur in May and June, the outbreaks edging north along with the frontier between the cold and warm airmasses.  Then there are the floods. Obscured by the savage fury of the tornados is the fact that this is shaping up as one of the most serious flood years ever along the lower Ohio and lower Mississippi. a heavy snow melt to the north is partly to blame; also, the colliding warm and cold air masses got stuck for weeks, causing local rainfall near the rivers to exceed 2ft in some places during april alone.  On the lower Ohio, just before it joins the Mississippi, they're talking about the worst flooding since 1937. On Monday night army engineers had to blow a hole in a levee, creating a mile-long breach that deliberately flooded thousands of acres of some of the most fertile farmland on earth - all to lower water levels upstream, and prevent the town of Cairo, which sits at the confluence of the two rivers, from being submerged.  Cairo now seems safe but more levee breaches downstream may be necessary. There, the benchmark year is 1927, when in one of the worst natural disasters in US history, 27,000 square miles (over half the land area of England) were flooded, mostly in the states of Louisiana, Mississippi and arkansas, and hundreds of thousands were made homeless.  Could it happen again? Probably not, given the vast im 