The page gets pretty technical for those of us who are not atmospheric scientists, but near the bottom of the page he mentions “the batting average paradox” – which contains a surprising bit of math that any of us can appreciate…

“The batting average paradox. Able has a higher batting average than Baker in the first half of the season and also in the second half. You might think that that means that Able has a higher average for the season. But you would be wrong. Click here to see why averaging ratios can be misleading.”