I was talking to my (Argentine) fiancée about the difference between the past tense in Spanish and English and the topic of the imperfect tense came up. I gave the dictionary definition of the imperfect (habitual or repeated action, blablabla) and she gave me the example of "este invierno hizo mucho frío." She says it's correct and I trust her because she's a native speaker (and I have learned what happens when I contradict her...), but my instinct says that "hacia mucho frío" would be correct. What does everyone have to say about this?