Magnetic nanodot structures have significant potential in spintronic applications. The magnetism of nanodots are predominately influenced by external conditions such as temperature. While the magnetization reversal modes of sub-100 nm Fe nanodots has been reported, currently there is a lack of information about the temperature evolution of the magnetic properties of larger Fe nanodots. In this work, the magnetism of Fe/Ag thin films and nanodot arrays were comparatively analyzed over the temperature range of 2–300 K. A natively-oxidized α-Fe2O3 layer was formed at the Fe/SiO2 interface, and this oxide resulted in an exchange bias at low temperatures. The in-plane and out-of-plane magnetization reversal modes of nanodot arrays were revealed through the magnetic hysteresis loops’ temperature dependence. The contribution of exchange coupling between Fe and α-Fe2O3 was also identified through the temperature dependence of the coercivity, exchange bias, and DC susceptibility. Our results provide new insights towards understanding the magnetization dynamics in nanosized magnetic elements.