Very few people attribute the flood waters all to rain. Most consider that God broke up the fountains of the great deep.
But I'll take back about the 40 days and nights only being on Noah, it does sound like it rained on the earth 40 days and night. But even still, I wouldn't interpret that to mean that it rained continuously everywhere 24 hours a day. In Louisiana we'd get rain 5 days in a row, and much of that could be a constant downpour, but it still took breaks, an hour here and there.
Gen 7:11 In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened. 12 And the rain was upon the earth forty days and forty nights.