As the cold weather comes, the oil in the engine and gearbox gets thicker. It takes more power from the battery to turn the starter. Sadly, as the cold weather comes, the battery itself produces less power. The combination of the 2 results in bikes/cars becoming harder to start.
If a battery is new, and used regularly, it should see through a winter. However, as they age, they get worse.
I cannot recommend strongly enough the use of a batter optimizer/charger that can be left on all the time the bike is not in use (as opposed to a battery charger, that cant be kept on without long term damage). the optimizers condition the battery and make sure that its at peak performance all the time.
I went out to the garage to my bike, took the alarm off, turned the ignition on, a bit of choke, and hit the starter. She fired into life immediately cause the battery is good and strong.
If an electric supply is not to hand for you, solar powered optimizers are available. They obviously only work in the day, but with use, they should keep the battery in good enough condition to power the bike enough to start in a morning.
However, if you do not know the history of the battery, and it doesnt look new, it is probably a good idea to replace it. Get an optimizer at the same time, and you will be ensured of years of use out of it.