The decree covers all districts of the country more than 3,000 meters (9,800 feet) above sea level, as well as three regions in the Peruvian jungle that have registered strangely low temperatures in the last few weeks.
According to official figures, so far this year at least 409 people have died of pneumonia and ailments related to the cold weather, most of them younger than 5 years old (200 deaths) and over 60 years (158 deaths).
The emergency declaration, which has a duration of 60 days, covers districts in the regions of Ancash, Apurimac, Arequipa, Ayacucho, Cusco, Huancavelica, Huanuco, Junin, Lima, Moquegua, Pasco, Puno and Tacna, which in recent days reached a temperature of -24 C (-11 F).
A state of emergency was also declared in the jungle regions of Madre de Dios, Ucayali and Loreto.
The decree published Saturday also includes a series of measures that will allow regional and local governments to supply the affected populations with food and vaccines.
The armed forces were also called upon by Defense Minister Rafael Rey to carry out civic actions to help those populations most vulnerable to the cold.