According to a statement from IPMA, the yellow warning for the two islands of the Western group of the Azores will be active between 02:00 local time (03:00 in Lisbon) and 11:00 local time (12:00 in Lisbon) on Friday, due to "heavy rainfall, which may be accompanied by thunderstorms".
The yellow warning, the least serious on a scale of three, is issued whenever there is a risk situation for certain activities dependent on the meteorological situation.