Spring (April and May) and autumn (September and October) are the best times to visit. The weather is warm but not brutal, the site is green from winter rains, and the crowds are manageable. July and August are hot — temperatures regularly top 35°C — and the site has almost no shade. The ruins of the stadium and temple colonnades offer little shelter from the midday sun.
Winter is quiet and cool, with some rain, but the site remains open and you may have it nearly to yourself on a weekday morning. The Archaeological Museum is a good refuge in any weather. The village hosts small cultural events around the anniversary of the ancient Olympic Games in August, but there is no large-scale re-enactment festival.