The best time to visit Vancouver is summer, roughly June to September, when the famously rainy skies clear, temperatures are warm but rarely hot, the beaches and seawall come alive and the mountains are open for hiking. July and August are the sunniest and busiest, with the highest prices; May, early June and especially September offer nearly the same weather with thinner crowds and better value, making September a local favourite. Autumn and winter (October to March) are mild but wet and grey, with short days and frequent rain, though winter brings world-class skiing on the nearby North Shore mountains and at Whistler. Pack a waterproof layer whatever the season.
Vancouver is a very safe city overall, but the Downtown Eastside — a few blocks around East Hastings Street just east of Gastown and Chinatown — has highly visible homelessness, open drug use and street disorder that can feel confronting. It is a public-health crisis area rather than a place targeting tourists, and violent crime against passing visitors is uncommon; walk through with normal awareness by day, avoid it at night, and don't photograph people.
The main practical risk for visitors is petty theft: car break-ins ('smash-and-grabs') are common, so never leave anything visible in a parked car, and keep an eye on bags and phones in busy tourist spots, on transit and on patios. Use your accommodation safe and carry only what you need.
Much of Vancouver's appeal is outdoors, and the nature deserves respect: the Pacific is cold year-round with currents, mountain weather changes fast, and North Shore trails can be steep and remote with black bears present. Check conditions, carry layers and water, stay on marked trails, and tell someone your plan before longer hikes.