Kevin Myatt is The Roanoke Times' weather columnist.

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It's been a hot, dry year in Southwest Virginia. In the past 60 years, few have been drier, and none has been hotter.

2007 is virtually assured to finish as Roanoke's warmest on record. Through Friday, the year's average temperature was 59.2 degrees, making it only the second year since records began being kept at the Roanoke airport in 1948 with an average temperature at or above 59 degrees. The other was 1990 with an average of 59 degrees.

While there appears to be nothing within reason that can happen in the remaining few days to lower the year's average temperature below a record, 2007's rank among the driest years on record will depend on how much rain falls this weekend.

Before Friday's rain, Roanoke had 28.8 inches of rain for the year. Had the year been over then, it would be the second-driest on record -- only 2001 (24.94 inches) would have had less rainfall.

But Friday's rain and the potential for more precipitation -- rain, sleet or snow -- on Sunday probably will vault it past 1988 (29.66 inches) in the rankings.

Still, at 30 inches, the year's precipitation would be almost a foot below normal.

All but three of the 12 months in 2007 finished above normal in temperature.

August of this year was not only the hottest August on record, but the hottest month on record, with an average temperature of 82.1 degrees. The next five hottest months on record are Julys, and only one topped 80 degrees (80.2 degrees in July 1993).

This year also had the warmest March on record and the second-warmest October. January, May, June and September were each among the 10 warmest on record. December is on the bubble to finish among the top 10 warmest.

But there was also oddball February, which was the seventh-coldest February in Roanoke at 34.2 degrees.

A couple of other notable cool weather periods kept 2007 from being even hotter. An unseasonable cold spell through the first half of April offset a warm second half to keep it near normal, while a cool snap near the end of July dropped that month half a degree below normal.

So why was this year so hot overall?

There are a few different things to finger.

El Nino -- the recurring pattern of warm seas in the central Pacific -- in the early part of the year injected significant heat into the world's atmosphere, but it failed to deliver the moisture it typically does for the Southeast and mid-Atlantic states.

There is little doubt the heat and drought fed off each other, especially toward late summer and early fall when parched ground and vegetation continually absorbed heat, drying things out even further, thereby allowing more heat absorption, and so on in a vicious cycle.

I certainly think urban heat island warming -- concrete and other building materials of a sprawling city absorbing more heat and releasing it slowly -- is buoying Roanoke's official nighttime low temperatures on a consistent basis and therefore raising overall average temperatures. As I've pointed out a few times previously, there is a marked increase in daily records for highest low temperature starting about 1990, about the time commercial development began to surround the airport.

Then there is global warming.

The argument for global warming being a significant factor in this hot year locally would simply be that, of Roanoke's 10 warmest years on record, eight have occurred since 1990 and six since 1998, paralleling world and national trends.

The argument against it would be that Roanoke's period of record is too short and that a few warm years at the end of six up-and-down decades is not enough to rule out shorter-term natural cycles' being the cause.

Whatever the causes, we'll soon see if 2008 can continue any kind of trend, or if the mercury will back off a bit in the new year.

Something cold and wet

In talking about all this warmth and dryness, I would be remiss not to mention the possibility of something cold and moist coming our way Sunday.

It is possible that, after Friday's rainy system is followed by a cold front, another low-pressure system will move northeastward along that cold front Sunday, passing near us or to our east. The low may be able to throw some moisture into the cold air, which could trigger a wintry mix of precipitation.

Like every other wintry weather threat this month, it is a borderline situation, both in terms of temperature and the track of the low-pressure system. As of Friday afternoon, it appears to be mostly a cold rain with some sleet and snow mixed in, more of it the farther west you are in Virginia.

I'll be following our wintry weather potential on my Weather Journal blog at blogs.roanoke.com/weatherjournal/.