Complex sentence: The high daytime temperatures throughout the summer means that Penticton has on average the second most number of days in a year over (after Kamloops) and the city has the lowest amount of fog in Canada.
Split into simpler sentences: The high daytime temperatures throughout the summer means that Penticton has on average the second most number of days in a year over (after Kamloops). In addition, the city has the lowest amount of fog in Canada.