The best time to go to San Cristobal is during the warm-wet season from December to May.
During these months, the weather is generally sunny with occasional heavy showers, and the average air temperature is around 26°C. The ocean is also at its warmest, with temperatures around 25°C, making it ideal for swimming, snorkelling, and diving. The seas are typically calmer during this period, which can lead to a more comfortable experience for boat excursions around the island and to nearby dive sites.
This season is particularly good for those interested in marine life viewing. The warmer waters bring an abundance of fish, making underwater visibility excellent for observing colourful reef fish, sea turtles, and various rays. For those looking to see land birds, many species are nesting during this time, offering great opportunities for birdwatching.
Alternatively, the cool-dry season from June to November offers a different experience. While the air temperatures are slightly cooler, averaging 22°C, and the water temperatures drop to around 20°C, this period is known for its nutrient-rich currents. These currents attract larger marine animals, such as whales and the famous Galápagos penguins, which are more active during these months. If your primary interest is seeing these specific animals, this cooler season might be more appealing.
Ultimately, your choice depends on your priorities. For warm, sunny weather and excellent general marine life viewing, the warm-wet season is best.