Check out the weather forecast here for your travel destination. You would not want to pack incorrectly and be uncomfortable or spend money on items you may never need again. It is a good idea to check for the week ahead.
You will start by packing your basic wardobe, what kind of trip, business or pleasure, and add or subtract accordingly.
Then check the link below to see what you will need to add to your suitcase so that you will be prepared for what mother nature may throw at you.
For a forecast of showers you will need to add a raincoat, rain hat and umbrella. At some locations the wind can be so strong, when it rains that your better off with a hooded rain jacket than an umbrella, that may just turn inside out. In Italy a longer coat is best as it tends to rain in a way that gets your lower body wet.
If it is cool you may want to pack a warmer jacket
or sweater. Maybe you will need a warmer scarf or hat. What about boots...will you need them?
Check out that choice of shoes also… no open toes if it calls for rain.
I would rather layer than pack a lot of heavy clothes that I won't wear often.
If it is hot at your destination you will need more cool light weight tops and maybe shorts or Capri’s and sandals and less dark colours. You would also need a sunhat, sunglasses and sunscreen. If it is a really hot climate you may not need your light coloured sweater or your dark jacket. You should take two bathing suits, and maybe a sundress,but you do not want to pack anything that you do not need.
I like to be prepared but not pack for every possibility. That's why I always check here at the maps first.