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Experimental study was carried out to understand the tilt angle and temperature property of a flame and fire plume from a rectangular fire source in an unconfined space with the presence of external wind. The rectangular fire sources having the aspect ratio of 1/3, 1/5 and 1/12 were used. Two setting arrangements, the long side and the short side of the rectangular fire source faced to the wind direction, were adopted as the parallel and perpendicular arrangement, respectively. The fire plume axis was estimated based on the isothermal curves in the downwind temperature field. The concept of virtual source was employed to describe the relationship between the excess temperatures, ?T, and traveling distance normalized by Q2/5 for parallel arrangement and those by Q2/3 for rectangular arrangement, respectively. The decreasing modes of excess temperature along the traveling distance showed the similar but greater gradient than those from a circular/square fire source and from a rectangular without external wind, respectively. The tilt angle of the inclined flame from the source in parallel arrangement is greater than that from a circular/square fire source, and tilt angle from the perpendicular arrangement is much greater than that. The simple model to estimate the tilt angles for those fire source arrangements was established as the coupled function of Froude number, HRR, and characteristic source length. No obvious dependence on aspect ratio was recognized on the inclination behavior of the flame.