Fog shrouded a couple walking their dog on Malibu Beach in Dorchester  this morning.
Fog shrouded a couple walking their dog on Malibu Beach in Dorchester this morning.
Wendy Maeda/Globe Staff

Dense fog is still hanging heavy over parts of the state and Boston is just starting to see some rain, according to the National Weather Service.

Areas outside of Interstate 495 have the thickest fog, said meteorologist Alan Dunham. Visibility in Worcester is down to just a quarter mile.

Visibility at Logan International Airport has improved to five miles, up from a quarter mile this morning, he said.

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Boston police said a bicyclist was hit by a car at 8:02 a.m. at the intersection of Longwood and Huntington avenues. The victim declined to be transported to the hospital.

There was a motor vehicle accident near Science Park at 8:03 a.m., Boston police said.

And then just before 9 a.m., a bicyclist was struck at the corner of Centre Street and Chestnut Avenue in Jamaica Plain, Boston police said.

Rain is falling over eastern Massachusetts and Rhode Island, Dunham said. The rest of the afternoon will be mostly cloudy with isolated showers, which will become more frequent after midnight.

Southerly winds are driving moisture northward over cooler ground, causing the fog, said meteorologist Benjamin Sipprell.

The ground temperature dropped after last month’s spate of cold weather and today’s warm, moist air is mixing with the cooler surface, producing fog.

“November was a very cold month comparatively to the last 14 to 15 months here that we’ve been posting above-normal temperatures,” Sipprell said. “The fog right now is mainly across the Cape and Martha’s Vineyard, approaching up across the southeastern coastal plain and into Boston.”

The southerly flow of air will likely continue throughout the day, he said.

“Unless the sun can really get out and peek through, this can last into the midday hours,” Sipprell said. “It is possible to see this fog level stay with us through the evening hours.”

Foggy conditions are improving across the Cape and islands, but drivers in Boston will have to wait for the visibility to improve in the city.

Visibility in Nantucket has improved to seven miles, he said.

“Warm air will intrude across the region causing conditions to mix out and the fog to dissipate,” Sipprell said. “But with Boston so far north, it could take some time.”

Temperatures today will climb as high as 58 in Boston.

Sipprell said Bay Staters should enjoy today’s warm temperatures because the rest of the week will be cooler.

Wednesday’s temperatures will be in the mid-50s and the rest of the week will be in the 40s.