A lamp (6) includes a housing (5) mounted to a lamp post (4) and a light-emitting diode module (10) mounted in the housing (5). The light-emitting diode module (10) includes a metal substrate (21) and a plurality of light-emitting diode dies (221) mounted on a face (211) of the metal substrate (21). A jacket (11) has a coupling surface (112) engaged with the other face (212) of the metal substrate (21). A heat conduction pipe (12) includes a portion (123) received in a longitudinal hole (111) of the jacket (11). The coupling surface (112) of the jacket (11) has an opening (114) in communication with the longitudinal hole (111). A portion of an outer periphery (124) of the portion (123) of the heat conduction pipe (12) is in direct, thermal contact with the other face (212) of the metal substrate (21) through the opening (114) of the jacket (11) to absorb heat generated by the light-emitting diode dies (221). A finned heat sink (13) is mounted on another portion (121) of the heat conduction pipe (12) outside the jacket (11) to dissipate heat transferred to the heat conduction pipe (12) into the environment.