The Hague is a year-round city and its main attractions — museums, parliament, the Peace Palace — are not weather-dependent. The climate is mild and maritime, which means it is rarely very hot or very cold, but also rarely sunny for long. Rain is distributed fairly evenly through the year.
Summer (June to August) is the best time for Scheveningen — the beach fills up on warm weekends, and the terrace culture around the Binnenhof and Plein is at its most enjoyable. In June, the Noord Zee Jazz Festival takes place in Rotterdam nearby, and the Keukenhof flower gardens are at their peak in April and May. Prinsjesdag — the ceremonial opening of parliament on the third Tuesday of September — is one of the great Dutch public spectacles, with the royal golden coach and military procession drawing large crowds.
Winter is grey but not unpleasant. The Christmas markets and December light installations make a visit worthwhile, and the museum queues are significantly shorter than in summer.