there may be snow on the rooftop but there is fire in the furnace
An individual in advanced age, characterized by graying hair, may still possess ambition and vitality, especially sexual vitality.
ADJ
blazing, fiery, hot, red-hot | electric, gas | glass, steel | blast
VERB + FURNACE
fire
The factory workers had to fire up the furnace every morning before starting their shift.
FURNACE + VERB
burn, glow
The old furnace burned steadily throughout the cold winter night.
roar
The old factory's furnaces roared loudly whenever the workers fed them with fresh coal.