Locally, the declaration covers Chambers, Brazoria, Fort Bend, Galveston, Harris, Liberty, Matagorda, Waller and Wharton counties.
"Texans believe in taking action and always being prepared in the event of an emergency," said Governor Abbott. "Preemptively declaring a state of disaster will allow Texas to quickly deploy resources for the emergency response effort in anticipation of the storm's hazardous conditions."
Meanwhile, officials in Houston are preparing for the potential for heavy rain and street flooding.
The bayous could fill fast when the rain starts to come down. Hydrological technicians are checking elevations at bayous through Harris County to make sure they can take accurate measurements if and when the water comes.
More than 150 remote boxes stationed along the bayous allow real-time data to be transmitted live to emergency operations centers.
"Given what the models are showing with widespread nature of the rainfall that we're looking at and the rainfall totals that we're looking at, potentially all of our bayous and creeks would be a problem with this type of rainfall," said Jeff Lindner with Harris County Flood Control.
Harvey is expected to be what Harris County Flood District calls a long-duration event -- not just a burst of shows and flash flooding.
"Even if we don't see flooding Friday night, we don't see it Saturday, the threat is still there Saturday night, Sunday, and possibly even until Monday. We need people to be aware," Lindner added.
In Galveston, sandbags were already in place as families stocked up on food before Harvey hit.
"Just some bread and water and eggs. Some of the essentials. We've got kids, so we make sure we have stuff in the cupboards in the fridge," Rick Harper said.
The city, now under a storm surge watch, is bracing for torrential rains and extreme flooding.
"We've got all of our drainage crews out we're getting all the ditches cleared, trying to get all the drains cleared. We've got a lot of road construction going on on the island right now," a city official said. "We're trying to get all these construction sites tightened down just in the event that we get these heavy rains."
Some vacationers said they planned to ride out the storm unless told otherwise.
"I think the city will give us plenty of notice to get out of here if we have to," said Travis White, who was visiting from Fort Worth with his family.
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In the meantime, there's something you can do now to prepare. You've heard it a million times, but officials can't stress enough the importance of having a hurricane kit ready.
"We're in hurricane season. Prepare for it. Make sure your vehicle is at least half full of gas, make sure you have a kit if you live in an area if you'll be asked to evacuate, make sure you have the plans to do that," said Harris County Judge Ed Emmett.
With the remnants of Tropical Storm Harvey there have already been a lot of comparisons to Allison.
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