We experimentally compute the local heat transfer coefficient of blend refrigerant R-410A condensing inside horizontal rectangular multiport aluminium microchannels with hydraulic diameters equal to 0.52 mm and 1.26 mm. The refrigerant flows at near-critical pressure and the cooling air flows at high temperatures proper of hot climates. The experiments are conducted in a bespoke experimental facility and micro-foil sensors are used to measure the local condensation heat flux. The heat transfer coefficient is found to increase with the mass flow rate per unit area and the vapour quality and to decrease with the ambient temperature. Correlations available in the literature do not predict our experimental data satisfactorily because of our extreme operating conditions of high pressure and high cooling air temperature. A novel correlation is therefore obtained to successfully compute the Nusselt number for the condensing annular flow regime in our high pressure and high temperature conditions. (C) 2019 Elsevier Ltd. All rights reserved.