A risk for tornadoes will build over parts of New England on Sunday as a strong low-pressure system moves just north of the region. Keep a close eye on the radar through the day and make sure you have a way to get warnings the moment they're issued.

If a tornado outbreak killed a few hundred people, it would be remembered as a national tragedy. 

When a heat wave kills a few hundred people, it's the butt of countless jokes. 

That kind of nonsense shows up every time there's a prolonged extreme heat event and it's never any less enraging.

Extreme heat is one of the deadliest weather events in the world.

It's not a made-for-television disaster, but it's there whether we see it or not—silently claiming parents and grandparents, striking down perfectly healthy kids at football games, exacting a horrible toll on lower income people already struggling to make ends meet.

Heat waves are responsible for nearly half of all disaster-related fatalities. Heat has claimed an average of 188 lives per year over the past decade, compared to 103 flood-related deaths and 48 tornado-related fatalities over the same period.

Hot temperatures are relative. A 90°F day with humidity requires a level of acclimatization to handle. Someone living in Orlando, Florida, will have an easier time slogging through a scorching day than someone up in Burlington, Vermont. But not even everyone in the south has access to air conditioning. Extreme heat still kills and injures vulnerable people in the humid southeast and the deserts of the southwest.

It's not just a matter of what you're used to.

Lots of homes in the northern United States and throughout Canada still don't have air conditioning—whether by design or simply for lack of affordability. These homes become unbearably hot when the outside temperature climbs above just 80°F. Throw higher readings and some heat-retaining humidity into the mix and you have a recipe for extreme physical stress just trying to exist.

Heat waves also compound on themselves. Humid heat doesn't allow for any relief at night. Hot days spilling into hot nights wrap around you like a wet blanket when you don't have air conditioning to stay cool. Fans don't help in that kind of setup.

You're left with a situation where hundreds of thousands of vulnerable neighbors, friends, and family members are left to their own devices, hoping they see relief at the end of a days-long nightmare. They're lucky if they can get to a cooling center or visit someone for some relief from the stifling air. Many of them are forced to grin and bear the suffering, hoping that they're able to stay hydrated enough to stave off heat exhaustion or heat stroke.

Extreme heat is no joke.

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A tropical disturbance slowly moving into the western Gulf of Mexico will bring copious amounts of rain over the next couple of days, leading to a threat for flash flooding across coastal portions of Texas and Louisiana.

Forecasters expect the heaviest precipitation to fall over coastal Texas, where 5-10 inches of rain is possible through the middle of the week. Locally higher totals are possible. The region has famously poor drainage—especially the Houston metro area—so the likelihood of flash flooding during heavy rain is almost a given.

Remember, never try to drive across a flooded roadway. It's impossible to tell how deep the water is until it's too late, and the road may be washed out beneath the floodwaters. It only takes a few inches of moving water to lift up a vehicle and carry it downstream.

The slug of moisture is arriving with a tropical disturbance moseying into the western Gulf of Mexico. The National Hurricane Center gives the area a 60 percent chance of developing into a tropical depression over the next few days as it moves into the region.

Heavy rain is coming whether or not this develops into a named system. Some of the worst heavy rain events are the result of unnamed tropical disturbances—just look at what happened in Florida last week.

A tropical disturbance sent a vast amount of tropical moisture streaming over southern Florida. Persistent thunderstorms developed over the region, wringing out that moisture in the form of drenching rains that fell at several inches per hour at times.

Some areas wound up with more than two feet of rain, with the National Weather Service's latest precipitation analysis showing even more than that over the past ten days.

This latest tropical disturbance is a reminder that the Atlantic Ocean is open for business—and this season could mean business.

All major hurricane forecasts are calling for an extremely active hurricane season with predictions rivalling the busiest seasons on record. We could see more than 20 named storms this year if the forecasts pan out.

Extremely warm sea surface temperatures are driving those forecasts—and they're also likely driving the persistent heavy rain we've seen (and will soon see) across the Gulf Coast.

Warmer waters raise air temperatures over the ocean, allowing the air to hold more moisture than it would otherwise. It's likely that warmer sea surface temperatures are increasing the amount of moisture we're seeing over the region, which is enhancing rainfall totals in turn.

How unusually warm is the ocean right now?

Sea surface temperature anomalies are running 1-2°C above normal throughout almost the entire tropical Atlantic basin. 

Compare that to this time last year, where the extent and intensity of anomalies were still ugly, but a little less intense than we're dealing with this year:

It's worth noting that last year's very warm temperatures were able to fuel one of the most active hurricane seasons on record, overpowering the influence of El Niño which tends to subdue tropical activity in the Atlantic. 

This year, though, we've got even warmer waters and a La Niña in the Pacific, which is favorable to tropical development in the Atlantic. It could be a long, rainy summer. Hold on.

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The jet stream is moving to Canada—and you might also want to head north after seeing the temperatures on the way over the next week or longer.

A long-duration spell of warmer-than-normal temperatures will bathe the eastern half of the United States through the middle of the month as a ridge takes hold over the region.

Not only will this pattern crank up the heat, but it may finally shut off the Ferris wheel of severe thunderstorm outbreaks we've endured since early spring.

A devastating EF-4 tornado carved a scar through 30 miles of farmland in north-central Illinois on a muggy afternoon in April 2015. Two people died and nearly a dozen more were injured as the storm levelled neighborhoods in Rochelle and Fairdale, about an hour's drive west of Chicago.

Estimated winds reached 200 mph as the tornado swept homes and businesses clean off their foundations. Falling just 1 mph shy of scale-topping EF-5 status, it stands in the records at the strongest tornado to hit Illinois that decade. 

Here's an in-depth look at how a modest rain shower grew into a killer supercell over the course of just two hours.

We're at the beginning of a multi-day stretch of dangerously hot temperatures across the interior West, with temperatures in the triple digits expected for the deserts and California's Central Valley.

Excessive heat warnings are in effect for much of the region.

One active pattern after another sweeping across the U.S. this season will just keep on going as we head into the start of the Memorial Day weekend.

The Storm Prediction Center (SPC) issued a moderate risk, a level 4 out of 5, for much of Oklahoma and Kansas on Saturday as widespread severe thunderstorms are expected to develop across the region.

"Strong to violent tornadoes" are possible, the SPC said in its forecast on Friday afternoon.