The main islands of Choiseul, New Georgia, Santa Isabel, Guadalcanal, Malaita, and Makira have rainforested mountain ranges of mainly volcanic origin, deep narrow valleys, and coastal belts lined with coconut palms and ringed by reefs. The smaller islands are atolls and raised coral reefs, often spectacularly beautiful. The Solomon Islands region is geologically active, and earth tremors are frequent.

The islands' ocean-equatorial climate is extremely humid throughout the year, with a mean temperature of 27ƒ C (80ƒ F) and few extremes of temperature or weather. June through August is the cooler period. Though seasons are not pronounced, the northwesterly winds of November through April bring more frequent rainfall and occasional squalls or cyclones. The annual rainfall is about 305 centimeters (120 in.).

More than 90% of the islands traditionally was forested, but this has come under pressure from current logging operations. The coastal strips are sheltered by mangrove and coconut trees. Luxuriant rainforest covers the interiors of the large islands. Soil quality ranges from extremely rich volcanic to relatively infertile limestone. More than 230 varieties of orchids and other tropical flowers brighten the landscape.