Houston is suffering from a devastation of tragic proportions. Hurricane Harvey wreaked havoc on the Gulf Coast of Texas last weekend and has been sitting squarely over Houston for the past several days, causing severe flooding. Citizens and celebrities alike are coming together to help Houston, by raising money, donating clothing, food and other items, and even leading rescue efforts. (To find out how to get involved and where to donate, click here.)

You might be wondering why the city's residents didn't get the hell out of Houston before Harvey came barreling through. In order to get why they stayed put, you have to understand the city's complicated history with floods and evacuations. We've put together a timeline that breaks down Houston's reactive and proactive decisions in response to hurricanes—and why some of them led to more fatalities than the natural disasters themselves.

Hurricane Katrina

Aug. 28, 2005

On Aug. 28, 2005, Hurricane Katrina was identified as an incredibly dangerous Category 5 storm. New Orleans Mayor Ray Nagin ordered the first-ever mandatory evacuation of the city—around 80 percent of the 1.3 million residents evacuated. The storm made landfall at a Category 3 the next day, causing massive destruction, and killing hundreds.

Katrina ended up displacing over one million people from the Central Gulf Coast, creating the largest diaspora in U.S. history. According to the Washington Post, as many as 250,000 people from New Orleans landed in Houston after the disaster, and anywhere from 25,000 to 40,000 people made the city their home.

Hurricane Rita

Sept. 21, 2005

Not even a month after Katrina, Hurricane Rita came along. The storm developed into a record-breaking Category 5, putting everyone in southeast Texas on alert. As Rita's power rapidly gained intensity and unpredictability, the forecast worsened.

Former Houston Mayor Bill White told city residents in certain areas that evacuations were voluntary, with mandatory evacuations to be implemented the next day for Houston proper; the advisory was put in place to give coastal residents the opportunity to leave using routes Houston evacuees would be using.

With such widespread panic, especially in light of Katrina, many residents didn't pay attention to the distinction between voluntary and mandatory evacuations. 

Sept. 22, 2005

Even though weather trackers suggested Rita's path was veering away from Houston, city officials proceeded with the mandatory evacuation. The voluntary evacuation was already underway, but in light of the forecast's significant day-to-day shift, the risk was seen as too high to leave to chance.

Mayor White told residents, "Don't wait—the time for waiting is over... don't follow the example of New Orleans." With that message in mind, residents disregarded the planned staggered evacuation, taking to the road immediately. With gas shortages that left numerous vehicles stranded, it didn't take long for heavy traffic to clog the roads leading out of town. Seeing the massive backup, Mayor White told residents to follow the news and use common sense if they were not in the mandatory evacuation area. It didn't matter at that point: by afternoon, there were 100-mile traffic jams.

By the end of the day, forecasters predicted the path of the storm would shift north, away from Houston, deteriorating. But evacuations were already in full force, and millions along the coast continued to flee in historic numbers.

Sept. 23, 2005

Hurricane Rita deescalated to a Category 3 hurricane by the afternoon. Officials from Houston TranStar, Harris County’s transportation and emergency management center, reported seeing almost no movement on Houston area freeways.

Among the many to voluntarily evacuate were Brighton Gardens nursing home residents from nearby city Bellaire, Texas. The bus carrying the senior citizens hit the road the previous day, en route to Dallas. After a 15-hour trip, the bus caught on fire after residents' oxygen canisters exploded. 24 people died.

Sept. 24, 2005

12 hours after making landfall, Rita deescalated from a Category 3 hurricane to a tropical storm. But the panic had already settled in: an estimated 2.5 million people attempted to leave the city nearly simultaneously, leading to the most intense state of gridlock in Houston history. Drivers sat in standstill traffic for 20-plus hours, and some fights even broke out on the highway. All told, more than 100 evacuees died in the mass exodus of complications from heat stroke and dehydration. The casualties from the storm itself paled in comparison, amounting to less than 10.

Hurricane Harvey

Aug. 24, 2017

Harvey officially became a hurricane. Texas coastal communities in its path are urged to evacuate. By the end of the day, it is upgraded from a Category 2 hurricane to a Category 4.

Aug. 25, 2017

Harvey, still a Category 4 hurricane, made landfall on the Texas Gulf Coast, causing damage to cities like Rockport and Corpus Christi. Heavy rains befell cities in the state's southern regions.

Aug. 26, 2017

Harvey is downgraded to a Category 3, then further to a Category 2, then 1. While the storm weakened, forecasters predicted potentially catastrophic flooding in the coming days. Harvey is eventually downgraded to a tropical storm.

Aug. 27, 2017

Devastating floods pour into Houston, leaving thousands of people seeking higher ground. The U.S. Coast Guard reports saving more than 1,000 people.

Houston records nearly 25 inches of rain by this day, leading Houston Gov. Greg Abbott to request 3,000 National Guard and State Guard members help save residents of the city. 

Kam Franklin, lead singer for the Suffers and Houston resident, applauds the decision to not evacuate, saying the city's mayor ultimately saved lives.

Aug. 28, 2017

Officials reported more than 6,000 people were rescued by police and the Coast Guard since the storm hit. Countless more were rescued by good Samaritans. Harvey, which dumped 30-plus inches of rain in some places, increased in intensity as it drifted back over the Gulf of Mexico. 

Aug. 29, 2017

Harvey hovered over the gulf as a tropical storm, leading forecasters to predict it will turn back toward southeast Texas. Numerous people were reported missing, and several were reported dead. Hundreds of thousands of Houston residents remained without power.

President Donald Trump traveled to Corpus Christi and Austin for on-the-ground briefings on disaster relief, but did not visit Houston. Houston Mayor Sylvester Turner imposed a curfew on the city to curb looting efforts, and federal and local authorities reported somewhere near 13,000 rescues since the storm hit.

Aug. 30, 2017

As of Wednesday, Harvey is still a tropical storm. It made a second landfall in western Louisiana, where forecasters anticipate between 5 and 10 inches of rain. The New York Times reports up to 30 deaths in Texas so far; dozens, if not hundreds or thousands, are still awaiting rescue.