ELI5: Why does Irma have widescale evacuation while Harvey didn't have one?

Hurricane Katrina the mayor does not issue a evacuation till Landfall is expected In less then 24 hours. With the miserable response to Katrina still the focus of national attention comes Rita and the evacuation goes horrible wrong. 3.7 million people evacuated at the same time. Galveston County orders a mandatory evacuation that urges residents to leave in a staggered sequence based on zone. Houston, a pass through city for Galveston evacuees, Then the Texas Governor tells anyone near the coast now’s the time to leave. Mayor of Houston urged residents to evacuate the city, telling residents, "Don't wait; the time for waiting is over," reminding residents of the disaster of New Orleans. By the time Jefferson County began their mandatory evacuation, local roads were already full. 47% of the people not even in a evacuation zone left. the contraflow plan was then ordered and took 8 to 10 hours to implement. And that stopped the gasoline tankers with motorists running out of gas. The combination of severe gridlock and excessive heat led to between 90 and 118 deaths including a bus from a nursing home not in a mandatory evacuation zone that caught fire and 24 people perish. Texas now is Shelter in place or nearest safe place. Florida is so flood prone The plan is you’d better get out of Dodge. That could mean a nearby shelter but people keep going till they feel safe.

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