TL;DR: Yes, plants use water and nutrients at different rates depending on temperature. Warmer months mean more water is consumed relative to nutrients, so your solution may need diluting. Cooler months have the opposite effect.
Why seasons affect nutrient needs
Plants lose water through their leaves (transpiration) at a rate that increases with temperature. In warmer months, more water evaporates, which can concentrate the nutrients left behind in your reservoir. In cooler months, less water is lost, which can lead to the nutrient solution becoming too diluted relative to the water level.
In summer
Your reservoir will deplete faster. When refilling, add water in a slightly higher ratio to nutrients than usual to keep the EC level balanced.
In winter
Plants consume less water relative to nutrients. When refilling, lean towards a slightly more diluted solution to avoid over-concentrating.
The most accurate approach
Use an EC meter to measure nutrient concentration before and after each refill rather than guessing. This removes the seasonal uncertainty and gives you precise readings regardless of the time of year. We sell these in-store.
Growing indoors reduces the effect
If you are growing indoors with Gathera products, temperature fluctuations are much less pronounced than outdoors. Seasonal swings in nutrient requirements are smaller, though still present.