Smouldering peat fires are the largest fires on Earth, destroying an important ecosystem, and releasing large quantities of smoke, which is responsible for health issues and carbon emissions. Here we study the influence of wind direction (forward, perpendicular, and opposed) and slope (uphill, side hill, and downhill) on multidimensional smouldering spread, using a shallow open reactor. These conditions are known to be controlling variables in spread dynamics of flaming wildfires; however, wind and slope are rarely studied for smouldering wildfires. We conducted 21 experiments and compared the data to an additional 15 experiments from the literature. Where airflow was concurrent with spread (forward wind and uphill), both wind and slope increased the horizontal and in-depth spread rates by up to 101% and 32%, respectively, from quiescent and flat conditions. When airflow was perpendicular to spread (perpendicular wind and side hill), horizontal spread rate was increased by wind (up to 21%), but was negligibly influenced by slope. Airflow opposite to the spread direction (opposed wind and downhill) resulted in a negligible change in horizontal spread with wind, but a decrease in horizontal spread of up to 40% due to slope. We also found that spread in any direction on a slope can be evaluated as a function of the angle of the spread relative to the horizontal plane, regardless of the slope of the terrain. Our findings provide new insight into important field conditions affecting smouldering wildfires and provide a better understanding of their spread.