December in Turin, Italy, brings average daily highs of 9°C and overnight lows of 2°C in the 2016–2025 historical record. Warm layers deserve space in the bag. Keep longer outdoor plans easy to adjust, and allow places to stop between walks so that a colder day does not determine the whole itinerary.
In the record, at least 1 mm of rain or snow falls on 6 of 31 days on average, a daily chance of 21%. Leave some freedom to swap an outdoor day with a sheltered one. There is no need to read the average as a fixed number of lost days; it says nothing about how long rain lasts on each occasion.
The calculated day length, sunrise to sunset, averages about 9 hours. Sunshine averages 6 hours a day. Use the daylight window to plan the length of excursions, and check local sunrise and sunset times for the dates of your stay. Sunshine is a separate measure, and those hours need not arrive in one uninterrupted stretch.
For a culture-focused visit, group the places you want to see into manageable areas, with time between stops. Check each venue's opening dates before fixing the order. If food is a reason for the trip, leave time around meals rather than filling every gap with another journey. Check the places you choose for current opening hours.
The following month, January, has a similar average daily high of 9°C. Its historical rain-day chance is 20%, compared with 21% this month. If your dates are flexible, compare those trade-offs with the kind of days you want. Neither set of averages predicts the conditions of one particular holiday.