Kevin Myatt is The Roanoke Times' weather columnist.

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The concept of "normal rainfall" is a something of a fallacy.

Climate normals are the average of extremes and vary somewhat depending on the time frame used. In general, though, it is reasonable to expect a little more than 40 inches of rainfall each year in Roanoke.

Using the current data accepted by the National Climatic Data Center, Roanoke's normal annual rainfall is 42.49 inches, based on the 30-year average from 1971 to 2000. Using the old 1961 to 1990 data set, the city's normal annual rainfall was 41.13 inches.

Yet, looking at nearly 60 years of data from mid-1948 to the end of 2007, the annual average is 40.37 inches.

But whichever exact figure is used, it's obvious it doesn't take a lot of heavy rains to reach normal over the course of year -- less than an inch a week, in fact.

Eight-tenths of an inch a week will get us near 42 inches. One-third of an inch every three days gets us close to 40 inches.

In reality, rain never comes that evenly. But this month, it's been about as close as it gets. About every three or four days, there has been a new rain, never torrential. As a result, with 2.33 inches through Saturday, April is still about one-third of an inch above normal in rainfall for Roanoke.

A new round of April showers may be under way to start the week as you read this.