The second conditional is for an unexpected/impossible hypothetical present or future and the hypothetical consequence.
- If it snowed tomorrow, the schools would close, and I would have to stay home with the children.
alternate (If it were to snow tomorrow, the schools would close, and I would have to stay home with the children.)
The third conditional is for a hypothetical past and a hypothetical consequence. It is sometimes used to reproach people.
- If it had snowed yesterday, the schools would have closed, and I would have had to stay home with the children.
- If the hurricane had landed 100 kilometres to the south, it would have hit Miami and (it would have) caused major damage.
- If the hurricane hadn't landed in a mostly rural area, it would have caused major damage.
- If you had studied more, you would have passed your exam/you wouldn't have failed your exam. (reproach)
- If you hadn't partied so much, you would have passed your exam/you wouldn't have failed your exam. (reproach)