Wear light clothing and dress in layers. Temperatures can range wildly, especially at higher elevations or in the prairies (where 20 C or 50 F degree variations in a day are not unusual). Start with a cotton T-shirt, maybe another shirt, a wool sweater and a nylon or Gortex™ windbreaker. In cooler seasons, a pair of gloves will keep your hands warm. Always wear a cycling helmet: in many provinces it's now the law. On cooler days, wear a toque underneath, on warmer days a wet cloth to help you keep cool.
Mosquitoes and blackflies are a problem for cyclists, so you should use an insect repellent high in DEET. Avoid wearing scents, including colognes or scented soaps or shampoos. Do wash, though, as many bugs are attracted to the smell of perspiration.
Packing for a Cycling Trip
When packing for along trip, plan your load carefully. Use panniers (bags that hand alongside your wheels) to keep your center of gravity low, packing more on the rear panniers to keep load off the front steering wheel. Use handlebar bags for items you need during a tip, like maps, water, energy snacks. Keep bulky items on your rear carrier, attached by elastic bungy cords. Keep your bike locked up when unattended, even in small towns.
Repair and spare part items: