I'd be careful with a January wedding in Houston, keep in mind yes it could be 80 but it could also be 40 with freezing rain/sleet...you never know. I considered having mine outside but it's just too big of a risk IMO even for my spring wedding. Houston weather is so unpredictable and unless you don't mind a little rain/cold you don't want it to be ruined.
I don't know how much you want to spend or how big/formal you are planning, but I would look into the city parks depending on what part of town you live in. If you want something nicer, I've seen a few venues that can do the ceremony outdoors then have a room for the reception inside.
If you do go for an outdoor place, try to pick somewhere that has an indoor facility available too just in case you need to move indoors or some sort of backup plan. Good luck!