On rainy days when business is better, or when his luck happens to be in, he works longer to earn more, to make up for times when trade is slack.
凡事未雨綢繆的周孟德，甚至「雨時預存晴食糧」，在下雨天生意比較好或運氣較佳時多賺一點，以彌補生意清淡時的不足。