Water requirements change from season to season. In summer you tend to drink a lot of water due to sweating while in winter you might drink very less for obvious reasons.
Measuring water intake requirements in terms of cups or glasses might get confusing for some as ideally, one should drink at least 3 litre of water during winters and at least 4 litres of water during summers.
It might sound a lot but once you get used to it, it wont. The best way to start going about it to keep a sipper/bottle with you and keep sipping that water throughout the day.