Flow boiling in a microchannel with a pin fin was experimentally studied. Micro resistance temperature detectors (RTD) array was integrated inside a microchannel to enable local transient temperature measurement. The temperature measurements were synchronized with high-speed images to analyze boiling event and the corresponding transient temperature characteristics. Three distinct two-phase flow regimes were observed: bubbly flow, slug flow, and attached vapor cavity. Cyclic temperature fluctuations were observed during slug flow and it was related to local periodic vapor slug activities. In a single cycle, three distinct stages were observed: liquid wetting, film evaporation, and local dry out. These three processes were decomposed to calculate local heat transfer coefficient based on the experimental observation, as h(x,y) = tau(l)h(l) + tau(film)h(film) + tau(v)h(v) and the result was compared with available models in the literature. (C) 2019 Elsevier Ltd. All rights reserved.