One option worth considering is:
Quale est caelum?
Literally: "What is the sky/weather/air like?"
Aulus Cornelius Celsus writes in De Medicina 3.4:
Refert enim qualis morbus sit, quale corpus, quale caelum, quae aetas, quod tempus anni.
For it all depends upon the kind of disease, the patient's body, the climate, his age, and the time of year.
You could say:
Qualis tempestas est?
This usage appears in Historia Ecclesiae Gandershemensis:
…ut audirent [...] qualis tempestas esset
…that they might hear how the weather was.
However, literally, qualis means what kind of.
I have found the answer, and hereby provide a table for everyone’s benefit. Zel = Zelzer; BnM = Benedictine–Maurist; Bey = Beyenka.
Cross-reference table for the enumeration of the letters of Ambrosius (Aurēlius Ambrosius)
Michaela Zelzer, Sister Mary Melchior Beyenka, and Benedictine–Maurist numbers compared.