How heavy of a coat do I need to bring?

http://www.holiday-weather.com/rome/averages/

Jan avg hi about 57F - avg low 37 avg temp 46

But could be warmer and colder but not a whole lot usually.

Kind of like April weather in northern U.S. Layering is great - take one off when warms up -put more on when chilly - like mornings vs afternoons.

I've been in Rome several Januaries and always take a light jacket and have a sweat shirt and layers on heavy shirts. It can rain so bring some gear that is waterproof.

January is a great month to visit Rome. Agree with above. Medium, not heavy, jacket. Umbrella. Maybe one sweater for under the jacket.

Medium. Rain gear. Gloves. Scarf. Boots, maybe. Sweater or fleece.

It doesn't often go below freezing, and rarely snows. Damp, chilly weather is common, but sometimes the month is mostly bright and sunny.

Look at a forecast before you leave.

Wonder if as several years ago when I was in Rome when it was raining a sea of umbrella vendors appeared like magic everywhere - most looked like immigrants but if so no problem getting a cheap umbrella if need be. It was farcical to me - they were ubiquitous everywhere.