NEVER turn flashers on during a heavy rain storm unless you are STOPPED. As mentioned in the article, the glare of lights is amplified by the rain and turning on your flashers blinds other drivers. I was in extremely heavy rain once with severely limited visibility. When some drivers turned on their emergency flashers my visibility went to near zero. I could no longer tell where any cars were because my view was just filled with yellow and orange lights. It made a dangerous situation worse.
And never try to turn with your flashers on. Obviously a turn signal means nothing to other drivers when both your turn lights are flashing.