Kevin Myatt is The Roanoke Times' weather columnist.

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One year ago today, Roanoke recorded its first 100-degree reading in eight years.

But this week's predicted heat wave wilted on the vine.

Tuesday, which days ago I even touted as an outside threat to make 100 in Roanoke, didn't even make it to 90, the day's heating cut off by clouds blowing off strong thunderstorms in the Ohio Valley.

Unlike a year ago, when it seemed like every threat of hot weather materialized into multiple days of upper 90s with a few days above 100, this summer is stumbling and bumbling in trying to kick off a real heat wave.

Typically in July and August, the jet stream -- the shifting river of wind 5 to 8 miles high that steers weather systems -- stays primarily over Canada, making only a few shallow dips into the far northern states.

But repeatedly this summer, it has dipped farther south, through the Great Lakes and into the Ohio Valley.

That's happening again this week. The jet stream dip is allowing cooler air from Canada to push out the worst of summer's heat.

This particular jet stream dive will even push back much of the extreme heat the central U.S. has experienced, replacing it with below-normal temperatures in that region that could last much of the next two weeks, according to the Climate Prediction Center.

Several days of normal to slightly below-normal temperatures appear likely for our area. We'll get into the 80s most days and have lows in the 60s most nights. A "normal" day in Roanoke this time year sees a high of 87 and low of 65.

Rainfall threats will depend on whatever moisture can work up from the Gulf of Mexico against a weather pattern bringing winds primarily out of a dry northwesterly direction. This is not a pattern that will bring the kind of repeated, areawide general rains we need to alleviate a moderate drought that is about 3 years old now. Such widespread rain the next several days would probably require a tropical system, but that always carries the risk of getting too much rain too fast.

The jet stream pattern we've seen this summer would probably make for a cold, snowy winter were it January instead. At the peak of the cold season, the jet stream would probably dip to the Gulf of Mexico, and any disturbance moving through it would have the potential to trigger a winter storm.

Winter fans can wonder if it's a sign of things to come or a wasted pattern at the wrong time of year. But for now, cold weather folks will just have to be content with an August that isn't quite as sweltering as it could be.