Leeds is a northern UK city located to the east of the Pennine hills. The Pennines afford some protection from the westerly gales which means it's got a lower rainfall than the city of Manchester or the Lake District. In summer it can reach the giddy heights of 30c or beyond and in winter can get down to minus 2 or 3. Like all locations in the UK (with few exceptions) Leeds has weather rather than a climate. Which means it can be like a pleasant summers day one minute and a raging squall the next. Pack your clothes with this in mind.
All of the city centre is covered in malls and undercover shopping. And it is good, high quality shopping. You are never more than a brief walk to the nearest coffee shop or in store restaurant.
The best time to visit Leeds is year-round. There is always something interesting going on whatever the weather.