The weather – the dynamics of the atmosphere – are chaotic in nature. Although the weather obeys a a number of physical – deterministic – laws, its dynamics are intrinsically unpredictable. The dynamics of a chaotic system are sensitive for its so-called initial conditions.
The weather is intrinsically unpredictable (source knmi.nl).
Despite the chaos and unpredictability, the climate in North Western Europe for example, also shows very regular yearly cycles; I refer to the yearly seasons: winter, spring, summer and autumn. These cycles can be attributed to tilted axis of the Earth, and Earth’s rotation around the sun.