Yellow rain warning


Joined Jan 15, 2015
OK, I can understand Yellow Warning but I have a question about this:
21:55 on Tuesday until 06:00 on Wednesday
Strong to gale force west to northwesterly winds will continue to affect parts of north Wales and northwest England overnight into Wednesday. Gusts of 45 to 55 mph are likely, mainly in coastal districts and over hills. Expect some localised transport disruption with some trees perhaps uprooted. Large waves and spray will affect some coasts. This is an update to the warning to shrink the area to parts of north Wales and northwest England but extend the end time until 0600 Wednesday morning.
Why are the gust expressed in MPH (Miles Per Hour) rather than km/h Kilometers Per Hour?