Liberia is one of the wettest countries in the world, with the heaviest rainfall occurring from May to October. The country’s average annual rainfall exceeds 2,500 millimeters (mm). Rainfall is highest along the coast, but decreases towards Liberia’s interior plateaus and low mountains, where average rainfall reaches approximately 2,030 mm per year. Southern areas of the country receive rain year-round, while the rest of the country experiences two seasons due to the West African Monsoon. The wet season typically occurs in the summer months between May and November, with average temperatures of 25°C. The dry season typically occurs in the winter months, December to April. The dry season is dominated by the harmattan winds with average temperatures between 24 to 27°C. Relative humidity reaches 90%-100% during the rainy season and 60%-90% during the dry season. The annual temperature for the country is 25.7°C, with observed monthly temperatures ranging between 23.9°C (August) and 26.8°C (March). Mean annual precipitation is 2,467.07 mm and mean monthly precipitation of the country varies from 27 mm in January to 408 mm in September. Rainfall occurs throughout the year, with peak rainfall occurring from June to September, for the latest climatology, 1991-2020
- In Liberia, the mean annual temperature has increased by 0.8˚C between 1960 and 2006, an average rate of 0.18˚C per decade.
- There is insufficient data to determine trends in daily temperature extremes for all seasons, the available data does show that the average number of ‘hot nights’ per year increased by 57 between 1960 and 2003.
- Significant decrease in the annual frequency of ‘cold nights’, which have decreased by 18 days per year. This rate of decrease has been observed to be most rapid in March to May period.
- Mean annual rainfall over Liberia has decreased since 1960, however, it remains unclear if this is a long-term trend or due to the variability in rainfall for the region.