First of all, it has to be said that the only predictable thing about the Guyanese climate is its unpredictability.
However, there are some discernable patterns. There are two rainy seasons: early May to mid July and late November to late January. The May/June rains are more “reliable” than the December/January rains. Having said that, January in 2005 was exceptionally wet and there was extensive flooding! The February to April “dry” season isn’t usually as dry as the August to November “dry” season, and the two driest months are September and October. As a rough guide, Georgetown gets (on average) 2253 mm of rain per year.
This is the only predictable feature of the weather. It is hot all the year round – temperatures seldom rise above 33 degrees (Celsius) during the day, or fall below 25 degrees (Celsius) during the night. Bear in mind that those are shade temperatures, so the actual temperature that you feel will be much higher if you’re in the sun, although a steady north-easterly wind off the Atlantic takes the edge off the heat on the coast.
When to go?
Most visitors, to Guyana, will want to see some of the many waterfalls such as Kaieteur and Orinduik – the best time to see these is when they are at full pelt at the end of the longer wet season. For that reason, I would recommend going in late July or early August. On the other hand, if you want to see some cricket, then wait till September or October.
Take all that I’ve said about the rainfall patterns with a pinch of salt. It can rain incessantly during the dry seasons while the sun can shine endlessly during the wet seasons.