Located toward the east; or (of wind) blowing from the east.
From Old English 'east' plus '-erly' (directional suffix from '-ern'). This standard English directional adjective has been in use since before 1400.
English's directional adjectives (easterly, westerly, northerly, southerly) pack two meanings into one word—both location AND wind direction—which is why weather forecasters use them so precisely.
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