The noun "mano" is feminine, LA mano, LAS manos... Not all feminine nouns finish with an A.

In this case "heladas" is an adjetive, and means very, very cold. Male singular: helado Male plural: helados Female singular: helada Female plural: heladas Manos is a female plural noun, so "heladas". In Argentina "helado" as a noun means "ice cream". Pay attention!! ^-^

mano , or manos , it´s a feminine word , it doesn´t matter if it´s a man´s hand

Spanish has no rules for masculine or feminine. In this case, "mano" is feminine. Sorry, just learn it