"a long, hot summer"
Translation:صَيْف حارّ طَويل
It doesn't really show in this example, but both in Arabic and in English the order is basically the same: the most defining adjective (concepts like nationality, material, color) comes closest to the noun, the least one farthest. Arabic and English happen to have the opposite order of noun and adjective, hence you basically reverse the English order - but the principal is the same. This is btw. 'quite' universal, check out the English Wikipedia article on adjectives.
In English, when each of two adjectives modifies the same noun, we put comma between them. For example: "a long, hot summer". But, there's an exception when the first adjective modifies the combination of the second adjective and noun. For example: "traditional political institutions".
(Good, E., n.d.)