You can check absolute differences between both factors, add them, and search for the lowest sum possible.
But You need to define similar
more precisely.
Let's say temperature is twice more important than falls, you'll give a factor 2 to temp
, and a factor 1 to falls
. Then use this kind of query :
SELECT day
FROM weather
ORDER BY (
2 * ABS(temp - 14)
+ 1 * ABS(falls - 0)
) ASC
LIMIT 1