Best time to climb Ol Doinyo Lengai

The best time to climb Ol Doinyo Lengai is the long dry season, June to October, with a second good window in January and February. Just like Kilimanjaro, Mount Meru, going on safari, going to Zanzibar, the best time to climb Ol Doinyo Lengai is during the warm and dry season of January, even mid-December to February or mid-March. Roads into Lake Natron are firmer then, the ash slopes grip instead of turning to mud, and the midnight start is more likely to end in a clear sunrise. The mountain can be attempted in other months. It is just more likely to be closed by weather, slick scree, or an impassable escarpment track.

Dry season: June to October

This is the reliable window. Rainfall at the lake drops to very little, often around 8 to 15 millimetres in the driest months, and the murram tracks from Mto wa Mbu and the Longido side stay firm enough for a 4×4. Daytime temperatures at Natron still run hot, commonly the low-to-mid 30s °C, which is why the climb remains a night ascent. Nights are the coolest of the year, about 17 to 18 °C at the lake in July and August, so the rim before dawn is chilly and worth a fleece.
July to September is the pick if you want one fortnight. Skies are generally clear, the cone is more often open, and flamingo numbers on the lake tend to be easier to see, though breeding itself is irregular and tied to rainfall and salinity. October stays mostly dry but starts to warm, and the first short-rain showers can appear late in the month. Camps are busier in these months than in the rains, but Lengai is never a crowded mountain.

Short dry spell: January and February

January and February sit between the rains and are a legitimate second season. Slopes are usually dry and the roads are mostly passable. The drawback is heat. Basin temperatures often reach the high 30s °C and can exceed 40 °C, so the descent after sunrise is harsher than in July. Start on time, carry the full three to four litres, and do not treat a late summit as a small delay. Views are often excellent. Dust on the drive is part of the bargain.

When to be careful

The long rains, March to May, are the months to avoid if the climb is the point of the trip. April is the wettest stretch on the approach. Clay sections of the rift road become slick or briefly impassable, and wet ash on a 40-degree cone is a poor surface in the dark. May eases, but it is still a gamble compared with June.
The short rains, mainly November and sometimes into December, are a middle case. Storms are often afternoon affairs, crowds thin out, and the country turns green. A climb can still happen. It can also be postponed by a washed track or greasy scree. Book it only if the operator is willing to move the summit night, and if missing the rim will not wreck the trip.
The volcano is a separate calendar. Eruptions do not follow the rains. A dry-season week can still be closed because the northern crater is active. Ask the camp the week you travel, not only when you book.

How to choose

Choose June to October if you want the highest chance of a completed climb and a tolerable descent. Choose January or February if that is when you can travel, and treat heat as the main risk. Leave March to May for a lake visit only if you are relaxed about not going up. Whenever you go, keep one spare night at Engare Sero. On this mountain the season gets you to the trailhead. The spare night is what lets you wait out a clouded dawn or a guide’s decision to hold.

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