We investigated the effect of feed temperature on organic fouling of reverse osmosis (RO) membranes. Experiments were conducted over the range 27 < T < 40 C, relevant to feed temperatures in arid, near-equatorial latitudes. Fouling by alginate, a major component of extracellular polymeric substances, was investigated at the nanoscale by means of AFM-based temperature-controlled colloidal-probe force spectroscopy (CPFS). The CPFS results, complemented by interfacial property characterisation (contact angle, surface roughness and charge) conducted under temperature-controlled conditions, enabled us to rationalize the observed fouling kinetics in cross-flow fouling experiments. We observed less severe flux loss at 35 C (J/Jo = 75%, t = 24 hr) compared to 27 C (J/Jo = 65%), which is due to weaker adhesion forces with rising temperature. The observed variation in the magnitude of adhesion forces is consistent with the temperature dependence of hydrophobic interactions. At 40 C, the observed flux loss (J/Jo = 68%) was similar to that at 27 C, despite the fact that adhesion forces are relatively weak (and similar to those at 35 C). Analysis using a series-resistance model shows that the foulant layer hydraulic resistance is equal at 35 and 40 C, consistent with the CPFS results. More severe fouling was observed at 40 C compared to 35 C, however, due to the higher water permeance at 40 C, which resulted in a greater flux of foulant to the membrane. Our experiments further show that the fouling layer develops within ~2 hours, during which the flux sharply decreases by 26% at 27 C, 19% at 35 C, and 22% at 40 C; thereafter, flux losses are small and temperature independent.CPFS experiments show that this behaviour is due to the foulant layer, which results in weak, often repulsive, and T-independent foulant-foulant interactions, which hinder further foulant deposition.