6. (10 points) During the 2014 Beijing APEC meeting, the Beijing-Tianjin-Hebei region implemented traffic restrictions and shutdowns of polluting enterprises to ensure that air quality reached a good level. After experiencing three fog and haze events in a month, Beijing's air quality reached level one on November 3, which people called "APEC Blue." In 2013, the number of days with good air quality in Beijing only accounted for 47.9%. In the first half of 2014, with a 30% reduction in emissions, the number of days with good air quality increased by 20 days compared to the same period in 2013. To achieve the goal of increasing the number of days with good air quality by 20% for the whole year, the second half of the year needs to see at least an increase of \qquad days with good air quality compared to the same period in 2013.
【Solution】Solution: $365 \times 47.9 \% \times 20 \% - 20$
$$
\begin{array}{l}
\approx 174.8 \times 20 \% - 20 \\
\approx 35.0 - 20 \\
= 15 \text { (days) }
\end{array}
$$

Answer: In the second half of the year, the number of good weather days needs to increase by at least 15 days compared to the same period in 2013. Therefore, the answer is: 15.