Unseasonable rain showers have kept maypole dancing to a minimum for the first few days of May.  But longtime dwellers of the Central Valley know to keep their shorts and tank tops handy. It is going to be scorching hot soon.  Spring is effectively over.  Like a clock-watcher at the end of her work shift, spring is so out of here the moment the summer sun arrives, and nobody is going to see her mild days and chilly nights again until 2010. So forget looking up at the cloudy skies.  Look down on the ground.  Wildflowers -- or weeds, if you please -- tell us that summer is coming.  If you've done any crawling around in the grass in the last week or two, you'll have noticed that most wildfl