From the National Weather Service:
URGENT - WEATHER MESSAGE National Weather Service Boston/Norton MA 404 AM EDT Tue Jul 3 2018 MAZ022>024-RIZ008-031300- /O.NEW.KBOX.FG.Y.0024.180703T0804Z-180703T1300Z/ Barnstable MA-Dukes MA-Nantucket MA-Block Island RI- Including the cities of Chatham, Falmouth, Provincetown, Vineyard Haven, Nantucket, and New Shoreham 404 AM EDT Tue Jul 3 2018 ...DENSE FOG ADVISORY IN EFFECT UNTIL 9 AM EDT THIS MORNING... The National Weather Service in Boston/Norton has issued a Dense Fog Advisory, which is in effect until 9 AM EDT this morning. * Location...Cape Cod and the Islands * Visibilities...One quarter mile or less at times. * Timing...Until about 9 AM. * Impacts...Dense fog will cause dangerous driving conditions early this morning. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Dense Fog Advisory means visibilities will frequently be reduced to less than one quarter mile, for at least 3 hours. If driving, slow down, use your headlights, and leave plenty of distance ahead of you.