Snow emergencies have been declared in Boston, Cambridge, and Somerville. Here's the dirt on parking and getting around:

--T alerts: This should come as no surprise, but all T lines are experiencing delays of 30 minutes or more.

The MBTA website has been blinking in and out, but we did get an alert that the Silver Line Routes 742 (SL2) and 743 (SL3) are being diverted and that all buses are "omitting 88 Black Falcon Ave."

The Green E line is stopping at Brigham Circle due to--oh, boy--"auto gridlock." Route #39 buses can take you to Heath Street.

--From the Mayor's office in Boston: Do not park cars at "main arterials" or within 20 feet of an intersection, shovel out your hydrants, and do not throw back snow into the street. Regarding "main arterials," Allston/Brighton, Charlestown, Dorchester, Downtown, East Boston, Hyde Park, Roxbury, South Boston, and West Roxbury have the most. Get a full list of arterials by neighborhood from the City of Boston's website. Select your neighborhood from the dropdown list.

--Parking in Boston, from the Mayor's office: "During declared snow emergencies, discounted parking is available at several parking lots and garages to cars that display Boston resident parking stickers." Get a list of alternate parking areas from the City of Boston. Select your neighborhood from the dropdown list.

If you have any other questions about snow in Boston, contact the city's Storm Center hotline at (617) 635-3050.

Cambridge: A parking ban will start at 7:00 pm tonight according to the Cambridge Chronicle. Cambridge has also declared a snow emergency. Find out if you can't park on your street by looking at the city's snow emergency map. If you are affected or find that your street has been flagged, you can park at the Galleria Mall, the First Street Garage, the Green Street Garage, and the 52 Oxford Garage for free. More details are at Cambridge's city site.

Somerville: You can park on the odd-numbered side of the street only. The Somerville Journal adds that you can park in any municipal or school parking lot if you need to move your car. More details are available at the city of Somerville's website.

Image of snowfall in Somerville from Varmazis from photos tagged "Bostonist" on Flickr.