Tsavo West is accessible year-round, but conditions vary considerably. The dry seasons — January to March and July to October — are the best times to visit. Vegetation thins out, animals concentrate around water sources, and the tracks are passable without a 4WD. July to October also overlaps with the wildebeest migration in the nearby Mara, so if you're combining parks, this is the window.
The long rains fall from April to June, and the short rains from November to December. The park stays open through the wet season, and the landscape turns a vivid green, but tracks become muddy and wildlife is harder to spot in the thick vegetation. Birdwatching improves dramatically in the rains — over 600 species have been recorded in Tsavo West, including large flocks of migratory birds passing through.
Temperatures are warm to hot throughout the year, typically 25–35°C during the day. Evenings at altitude (Ngulia Lodge sits at around 1,600m) can be cool enough for a fleece.