Weather: Venezuela, Colombia, French Guiana, Guyana, Suriname

The usual ingredients of tropical climate – sharp moisture contrasts, temperatures that hang steady – come together in intriguing ways through the belt of countries across the north end of South America.

The Caribbean coast of Venezuela and Colombia is famous for its oddly dry climate, with striking differences in rainfall across short distances. Although the coast stays warm and humid year round, the easterly trade winds tend to parallel the shoreline, rather than blowing onshore. That – along with some large-scale climate mechanisms still being unravelled – makes the coast from Rio Caribe westward to northern Colombia far more arid than one might expect. Instead of rainforest, you're more likely to encounter scrubland or even cactus. Many spots along the coast, especially the peninsulas on either side of the Gulf of Venezuela, get less than 500mm/19in of rain a year. The amounts jump sharply just inland, particularly along the slopes of the Cordillera de la Costa (including Caracas), and Cordillera de Merida. At these elevations, humidity remains high, but temperatures are more moderate.

Across most of northern Venezuela, the rainy season, or verano, goes from May to November. There's a slight let-up in late June or July across the northwest due to the verano de St John (this region's equivalent of the Central American veranillo). The driest stretches of coastline get only sparse showers during the May-to-November period; their rains are actually focused from November into January (and even then, most days are dry). A few cool fronts from North America make it across the Caribbean into northern Venezuela from December into February, each bringing a spell of clouds and slightly cooler temperatures. The Venezuelan coastal ranges are also vulnerable to easterly waves approaching from the Atlantic. Usually arriving toward the latter part of the wet season, these can produce several days of torrential rain.

In December 1999, a catastrophic flash flood – the deadliest weather event in the recorded history of the Americas – killed some 30,000 people, as water tore through settlements that line the hills from Caracas to the Caribbean. Heading southward into the heart of Venezuela, the wet season tends to be more consistent. The vast grasslands of the Llanos, parched during the months of low sun, are inundated by torrential thunderstorms on most days from April to November. Even heavier rains fall across the Guiana Highlands, where the altitude yields somewhat milder temperatures. The Amazon lowlands extend from Brazil into southeast Colombia and southernmost Venezuela; here, you should be prepared for sultry conditions and a possible heavy thunderstorm most any time of year. The heaviest rains fall from April to July. Annual totals top 3000mm/118in across much of this area. Rainfall is also extensive as you move from Venezuela into the forests of Guyana, Suriname and French Guiana. The intertropical convergence zone (ITCZ) sweeps through this region twice each year, following the sun. The ITCZ tends to produce near-daily torrential storms as it shifts north (roughly April to July) and less-intense, but more-prolonged, nighttime rains as it passes to the south (November–February). Except on the easternmost Guiana Highlands, these countries are sweltering year round.

If it's rain you seek, you'll be hard-pressed to beat the Pacific coast of Colombia, which ranks with northeast India as one of the world's soggiest spots. As moist southwest winds – contrary to the usual easterly trades – encounter the Andes, they dump buckets of rain throughout the year along the coastal plain and adjacent slopes. Some points around Quibdo average more than 10,000mm/390in a year, and in 1936 the city itself scored a record for the Americas with 19,839mm/782in. There's method to this moist madness. Generally, the slopes get afternoon thunderstorms and lighter nighttime rains. The lower elevations typically get a period of light, steady rain from sundown to sun-up, with the bulk of the day frequently bright and dry – a convenient window for intrepid visitors who want to see the wettest spot in this half of the world.