Remus was born in 1960 and Tonks was born in 1973, so he would be 12–13 years older than Tonks. Tonks was in her 20s and Lupin was almost 40.
Sustained wind speeds around 20 mph, or frequent gusts of 25 to 30 mph. " No Discernable Threat to Life and Property from High Wind." The sustain wind speeds are non-threatening, "breezy" conditions may still be present. Note: In "High Wind" conditions, small branches break off trees and loose objects are blown about.
20 MPH is less than the average days wind speed in parts of the midwest. If YOU don't feel in complete control, then it's not safe. 20mph is normally OK, but what you need to find out is whether there will be higher gusts expected. It is usually the sudden gusts that can catch a driver unawares and make it dangerous.