We present the results of a search for long-duration gravitational wave transients in the data of the LIGO Hanford and LIGO Livingston second generation detectors between {\$} \newcommand{\OOneStart}{\~}September {\~}2015 \newcommand{\OOneStartShort}{\~}2015 \OOneStartShort{\$} and {\$} \newcommand{\OOneStop}{\~} January {\~}2016 \newcommand{\OOneStopShort}{\~} 2016 \OOneStopShort{\$} , with a total observational time of {\$} \newcommand{\OOneLivetime}{\~}d \OOneLivetime{\$} . The search targets gravitational wave transients of 10–500 s duration in a frequency band of 24–2048 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. No significant events were observed. As a result we set 90\% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. We also show that the search is sensitive to sources in the Galaxy emitting at least  {\~}10−8 {\$} \newcommand{\msuncd}_{\odot} c{\^}2 \newcommand{\msun}_{\odot} {\msuncd}{\$} in gravitational waves.