It depends heavily on a lot of factors, of course -- like what category Rita is when it hits landfall, how close the path of its eye passes to Conroe, whether it moves slowly across the area or zips through within a few hours, whether it's a very "wet" storm (dropping lots of rain) or not, etc.
But the good news is that Conroe is far enough inland that a major fraction of the hurricane's power will have been expended already by the time it reaches there. And of course the storm surge (one of the most destructive parts of a hurricane) won't be a factor at all that far inland.
If Rita doesn't get much stronger than a category 2, folks in Conroe will likely not experience much worse than a heavy-duty Texas thunderstorm (lots of wind, wind gusts, and heavy rain).
Hurricane Alicia made a pretty much direct hit on Galvenston, Houston, and Conroe back in the 1980's (I swear, that hurricane followed I-45 all the way from the Gulf Coast to Dallas), you might want to look up what happened to Conroe back then to get a feel for what Rita might be like for that area if it follows a similar path.
And if it "misses", even 20 miles either way can make a *large* reduction in the effects of the storm. I've lived through a lot of "near misses" with hurricanes where you wouldn't even know a hurricane was around if you hadn't been watching the news -- sometimes it was like a regular rainstorm, other times it was blue sky.
Many thanks for the insight, Ich. I'll do some quick research on Alicia for good measure. Thx. - OB1
Let's take a look at what the Houston area might be in for, depending on where Rita strikes...
Port Lavaca, and points south: Houston would probably get some much-needed rain showers and light winds, but nothing unmanageable. As a likely category-3 storm, Rita simply wouldn't have the oomph to cause widespread damage or flooding. One area of concern: Galveston's beaches. When Claudette struck near Matagorda Bay in 2003 as a category-1 hurricane, it destroyed 60 percent of some recently completed beach renourishment projects.
Matagorda County: Houston would see heavy rain and high winds. The rain probably will be less of a concern, as it takes a good 10 inches to cause appreciable flooding in most parts of the city. The winds, perhaps has high as 75 mph, would be more of a concern. Such winds could damage unanchored mobile homes, shrubbery, and smaller or older trees. Most power poles would probably survive. Tornadoes spawned by the storm could also cause havoc.
Galveston Island: Think Hurricane Alicia, which came ashore Galveston as a category-3 storm in 1983, with gusts up to 126 mph. The storm killed 21 people, destroyed 2,300 homes. The Red Cross sheltered 63,000 people. All told, in an era when there was considerably less coastal development, Alicia caused $2 billion in damage. Enough trees were blown down to fill a football field 1,200 feet high. The storm pushed the beach on Galveston's West End back by 150 feet in some places. Rita, if coming ashore in Galveston, could have winds near 100 mph over downtown Houston, enough to cause roofing and window damage to even well constructed homes. That's enough about Alicia, I think. It wouldn't be any fun.
Upper Texas Coast: Barrier islands here are already receding, and Rita would accelerate the process. Houston would be on the storm's drier side, although strong winds and rain would still be present in force. The scenario for this strike point is similar to Matagorda County.
Statement as of 5:00 PM EDT on September 20, 2005
Rita passing south of Key West, moving into the southeastern Gulf of Mexico.
Movement toward west near 15 mph. Maximum sustained winds 100 mph. Minimum central pressure 973 mb.
Hurricane force winds extend outward up to 45 miles from the center, and tropical storm force winds extend outward up to 140 miles.