O'Brien, Texas is a small town located in Haskell County. The climate in O'Brien is characterized by hot summers and mild winters. Summers are typically hot and dry, with temperatures often reaching the 90s Fahrenheit. Winters are generally mild, with temperatures rarely dropping below freezing.

Hydrology in O'Brien consists mainly of the Double Mountain Fork Brazos River, which runs through the town. It serves as a primary water source for irrigation and provides opportunities for fishing and boating.

As for outdoor recreation, O'Brien offers various activities. The Double Mountain Fork Brazos River provides opportunities for fishing enthusiasts, with catfish, bass, and sunfish being commonly caught. Camping and hiking are also popular in the area, with nearby parks and nature reserves offering scenic trails for exploration. For those who enjoy birdwatching, O'Brien is home to a variety of bird species, making it an ideal spot for bird enthusiasts.