Spring 2011 in London. These have been some of the hottest April days since records began. Taken by surprise, we can now behave as if it’s summer: short sleeves, barbecues, parks, chilled white wine. But there have also been recent examples of the devastating effects of sudden changes in the earth’s behaviour.
Introduce an unexpected change in the weather to your novel, and see how your character behaves. Have this change in the weather impel (or even force) them to do the unexpected, 
maybe something completely out of character, or something they’ve been meaning to do for a while and this sudden hailstorm, or heatwave, or tornado, or soaring temperatures, or drought shifts their world and makes them act. Think what kind of impact a sudden change in the weather has on you. Note: The more detailed your description of the weather, the clearer it’ll be to you what needs to happen to your character.
Start with describing this sudden change in the weather, look at the bigger picture, how are people around your character behaving? what is the impact on their surroundings? had they been expecting something else?