Weather can determine what activities we decide to do because it provides the conditions for any activity. For instance, if it is snowing outside, then surely you won't choose to go swimming. And if it's sunny and hot outside, you're more likely to go swimming than do some skiing!
Weather affects our life because it is key in producing food that we need, and also it can also cause us trouble, with storms like hurricanes, tornadoes, and tsunamis, but also with extreme conditions like droughts. It can even change the way we life. (Example: droughts cause people affected to save water and use it sparingly.)