Same as using the same flavour boilie 2 days running but the 1st day you catch loads and the second you blank, good old mother nature but as you can imagine there a so many different flavour of baits going into a lake that there will be good and bad baits, just have a good selection between sweet and fishmeal and high proteins. A drop in air temperature by 5 degrees would only drop water temperature by 1 degree, then this would effect the fish habits but then different depths of a lake would change this. Carp will bask in the sun as this warms the water temperature. Then you have to take into account air pressure, high air pressure front(as we know the sunny days) SW wind will improve the fishes feeding habits if the has been a low pressure front(as we know the rainy cloudy days) days before. we all know that the cold weather i.e winter time the fishes feeding habit slow down( the fishes natural habits telling it to slow down I.e feeding) as they move less so the body doesnt need to regenerate as much the warmer months. Plus I`ve read somewhere that 4 days after a full moon always seems to be good fishing, I will say this is 99% true as I have tried this quite a few times. As les said trial and error but take all these into account when planning a trip. I havent read back through this so I hope it does make some sense, couldnt care less about speling mistakes.