Weather Effects on Mobile Social Interactions Figure 10. Probability mass of the ratio of the number of connected strong ties to weak ties under different weather conditions. doi:10.1371/journal.pone.0045745.g010 1050hPa). In such conditions, people were connected with fewer strong ties as shown in Fig. 8. On the other hand, the influence of weather is more noticeable for peoples’ connectedness to weak ties within their network (Fig. 9). We found that the number of weak ties people were connected to, decreased under weather conditions that may be uncomfortable for people. This was observed with extreme temperature bands such as (5uC–10uC) and (30uC–35uC). Humidity bands of 20%–100% showed the same correlation. When there is little or no wind (0–5 km/h), we found that people were connected to 0.008 weak ties/hour via their mobile phones. When wind speed was stronger than 5 km/h, their average connectedness to weak social ties was found to drop to 0.001 ties/ hour. For air pressure, we discerned three distinct patterns. Firstly, for air pressure band of 1010hPa–1030hPa, the band that normal air pressure falls into, we did not see any differences in the number of weak ties that people were connected to. Secondly, at the air pressure bands of 1000hPa–1010hPa and 1030hPa–1040hPa (which are respectively lower and higher than the normal), we found peoples’ connectedness to their weak ties decreased when compared to the condition when air pressure is normal. Thirdly, at extreme air pressure bands (990hPa–1000hPa and 1040hPa– 1050hPa), we found that people were connected to very few weak ties (about 0.002 ties/hour). Given that the number of connected ties were found to decrease with weather conditions that are uncomfortable, we then sought to determine whether weak ties or strong ties were more influenced by uncomfortable weather conditions. This is because, as we have shown earlier, the total number of strong ties that people were connected to was less than the number of connected weak ties (as shown in Fig. 7(a,b) and also evidenced in [22][28]). Thus, to understand whether uncomfortable weather conditions had a stronger influence on connectedness to either kinds of ties, we had to compare the ratio of the number of connected strong ties to the number of connected weak ties under each weather parameters. The overall ratio of the relationship between strong ties and weak PLOS ONE | www.plosone.org 10 October 2012 | Volume 7 | Issue 10 | e45745