|Hurricane? What are the chances?|
- It can be important in its own right - eg, a hurricane.
- It can be important because the players need something from it - eg, a favourable wind.
For #2, when the players ask what the weather's like, roll a weather encounter directly and judge accordingly. If the weather indicated is "common" then it is not note-worthy - not unusually hot or cold, wind in the prevailing direction etc. Don't bother making an actual encounter chart for common weather.
If it's not important, don't waste time on it. Do not come up with a massive table which you roll on each day. The weather is "normal for this time of year in this place" unless the tables alert you otherwise.
Also: "earthquake" is not weather, not even in Greyhawk.