Rome in January - Clothing Hints

Any time you travel you should consider layers of clothing. Not just a heavy coat, but in January consider a light base layer (long underwear made of lightweight merino wool or silk), a long sleeve top, but not made of cotton. Bring a sweater, either button down or crew neck style. Thinking about it, a heavy coat - if you mean weight wise is not wise...a lighter down jacket or synthetic insulated jacket with a sweater or a fleece jacket under it would be warmer than a "heavy coat". jeans are fine, but you should think about waterproof footwear instead of tennis shoes, or as your walking shoes. Winter time consider a light hat (one that covers your ears) and of course a scarf for your neck..that will certainly help to keep you warm in cooler temps.
And perhaps even a lightweight pair of gloves for your hands. If your head and hands are protected, the rest of your body will stay warmer!

Rome's weather in January is generally mildly cold, sort like the SF Bay Area.
Expect highs in the low to high 50's during the warm hours of the day (10 to 15 Centigrade). Temperatures at night may drop to the 30's and low 40's (0 to 5 Celsius), however they rarely go below freezing point (32 F=0 C). As suggested, dressing in layers is key, because heavy coats will definitely be too heavy in Rome during the midday/early afternoon hours, when it's not that cold at all. Every time I go to Rome in winter I always end up carrying my coat in my arm during the day, like an umbrella. But at night and very early morning you'll need something heavier outside.

We actually enjoy Italy in November so what we do should apply for January. Dress in layers. We take rain pants to pull on over our pants and they act like a thermal barrier against cold. Easy to take off when you enter a museum so you don't overheat. Zip on zip off (I think there was a movie variation on this theme...:) Ditto for your upper body. Waterproof wind breaker, sweater, long sleeve shirt, t-shirt - done. Light weight gloves, knit scarf, knit cap. Everything crumples into your day bag as you shed clothing during the day. Reassemble as temp requires. Forget the heavy coat. Jeans, I'm not so hot for. Heavy but hey, if you have a soft worn pair more power to you. Tennis shoes are probably a loser with all the rain. Get a good pair of waterproof leather shoes (I wear leather mules). Stuff with newspaper at night. Plish Plash your toes aren't taking a bath. My husband wears tennis shoes but takes two pairs.