“Cold way” and “warm way” are terms I don’t hear much in the states, but they crop up constantly in places where Warré and National hives are popular.
Frames that run cold way are perpendicular to the hive opening. If you have a standard Langstroth box on a standard Langstroth bottom board, your frames are perpendicular to the opening, so they are cold way. The arrangement is thought to be cold because air coming though the hive opening can slice straight through the hive, traveling unimpeded between the frames.
Frames that run warm way are parallel to the hive opening. It is believed that the first frame of comb blocks the wind and keeps it from rushing through the hive, so this arrangement is thought to be warmer—or at least less drafty. However, bees have to travel further to get where they are going because there is no convenient corridor at the hive entrance—the bees have to go over, under, or around that first comb-filled frame.
The cold way vs warm way debate
Since Langstroth hives are rectangular, you cannot accidentally or easily change the orientation. But both Warré and Nationals are square, so you can place the frames in either direction by simply rotating the box a quarter turn.
If you check out some of the bee forums, especially those in Europe, you can read countless disagreements about which system is better for the bees. As with most things in beekeeping, no one agrees, and the arguments rage on and on while the bees don’t seem to care much one way or the other.
Those who keep bees in a Langstroth and want their frames to run warm way simply build a bottom board with the hive opening on the long side instead of the short side. Some beekeepers really like this arrangement because they can stand behind the hive and lift each frame straight up for inspection.
Warm way is easier for beekeepers
Normally, working a Langstroth from behind is awkward because you have to pick up the frames with one hand close and one arm stretched across the length of the hive. Bees object to this human arm from time to time as nearly every beekeeper has noticed. And even after you grasp the frame, you have to twist it around before you can see it properly, and then you have to untwist it to set it back in the hive.
The answer to this problem is to either work hives from the side or change to a warm way arrangement. Not only does this prevent reaching over the top of the hive, but the frames are closer to you.
Nowadays, with the popularity of screened bottom boards, I think the argument about the draftiness of cold way hives is losing traction. If you have a screened bottom, the airflow is coming up from beneath the hive during most of the year, so the amount of draftiness will be less influenced by the orientation of the frames. In the winter, if screened bottoms are closed, the warm way may be slightly warmer, but you can counter this by switching to an upper entrance during winter cluster.