Kevin Myatt is The Roanoke Times' weather columnist.

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Extreme heat. Canadian cool. Tropical downpours.

The atmospheric battle for the second half of August is on. We are smack in the middle of a scrum between three major players that will determine our weather for the rest of this month.

We're familiar with extreme heat after last week's torrid run of record hot afternoons and balmy nights.

The culprit, a large and dense high-pressure system, has drifted to the west and parked over the Southern Plains and lower Mississippi River Valley. On Monday, every official reporting station in Arkansas recorded a high of at least 101 degrees. So it's still dishing out the heat.

Meanwhile, a persistent upper-level low has been spinning over southeast Canada. This has kept cooler-than-normal weather in place over that region, extending into the northeastern United States.

Mount Washington in New Hampshire was at 37 degrees on Tuesday morning with 52 mph winds from the northwest. Think about that the next time the heat index creeps above 100.

Like a belt between pulleys, the jet stream is weaving between these features, as the high over the central U.S. spins clockwise and the low over Canada spins counterclockwise. That steers the jet stream generally through the Great Lakes region and a few hundred miles north of our region.

It's dipping just enough toward us, though, to steer a few cold fronts through. Two came through Friday and Monday, and it took both to finally whack the top off our heat wave. Tuesday was the first day of near-normal temperatures in more than two weeks.

We're caught in the push and pull between the hot high and cool low.

Over the next two days, the hot high will expand eastward enough to build our heat so that Thursday could be another upper 90s -- maybe 100 -- day like last week. But then, the low will help sling a cold front through for the weekend that will again pull our temperatures back from the extreme.

The next couple of weeks may well be like this, with sharp warm-ups over two or three days followed by a cool-down.

Thunderstorms are always possible in these clashes of heat and cool, but moisture is limited, so probably there will be no widespread rainfall events that we really need.

But didn't I mention tropical downpours?

Ah, yes. Entering stage right is the rogue player that could steal the whole show by this time next week.

Tropical Storm Dean is churning west through the open waters of the central Atlantic. It's got a long way to go before it's a serious threat to the U.S. We don't know how strong it will end up being, and there's always a chance it could weaken or curve out into the open ocean.

But many computer-model projections have this storm threatening the Southeast U.S. more than a week out, and conditions seem ripe for it to become a hurricane. (Tropical Depression Five formed in the Gulf of Mexico late Tuesday night. It will likely move toward Texas or Mexico.)

How bad a hurricane is it worth having to get much-needed rainfall into drought-parched areas of the Southeast?

It's a question we have some time to ponder over the hot, dry days ahead.