Aurora Borealis? Awesome idea. Might as well throw in some meteor showers
Never liked weather in OB. Too random'ish over the spectrum, I prefer distributed randomness that favors nice weather. Light rain should also be fairly common. Heavy rain not that common. And thunderstorms fairly rare (especially along the northern coast, but could happen - where I live we have maybe 5 days in the year with thunderstorms, so it's way too frequent in the game, in ALL games). Also changes from severe clear weather to light rain should be very gradual. I'd even go as far as separating between steady rain and rain showers (stratus vs cumulus). Powerful elemental spells to affect it would also be welcome. AI should try seek shelter (within reason naturally) and dress according to weather.
I'd like to see whiteout effects caused by snow blizzards, but I want them to be rare compared to normal snowing. Much more gradual changes in precipitation too, from very light and fluffy and severe snowing, but whiteouts only in mountains with severe snowing and high winds. Thunderstorms could deliver heavy rain, hail, and even hail stones on the rare occasion.