The best time to visit Cameroon are earlier November to mid-March, although you’ll have harmattan haze during much of this time. The worst months are July to October, when it’s raining, and many roads are impassable. The north has rains from April/May to September/October. The hottest months are March to May, when temperatures can soar to 40°C, although it’s a dry heat. The south has a humid, equatorial climate, with rain scattered throughout the year. Its main wet season is June to October, with light rain from March to June.
The best time to visit Cameroon is during the months of November to February. These particular months are cool and dry months. The only hitch is the dusty Harmattan that blows Saharan sand from December to February and visibility can be pretty low. May to November is the rainy season and much worse compared to the Harmattan. (http://www.journeymart.com/de/cameroon-best-time-to-visit.aspx)
Cameroon is Africa’s throbbing heart, a crazed, sultry mosaic of active volcanoes, white sand beaches, thick rainforest and magnificent parched landscapes broken up by the bizarre rock formations of the Sahel. With both Francophone and Anglophone regions, not to mention some 230 local languages, the country is a vast ethnic and linguistic jigsaw, yet one that, in contrast to so many of its neighbours, enjoys a great deal of stability.
With good infrastructure (think decent roads and functioning trains), travel is a lot easier here than in many parts of Africa. Still, you’ll miss none of those indicators that you’re in the middle of this fascinating continent: everyone seems to be carrying something on their heads, makossa music sets the rhythm, the street smells like roasting plantains and African bliss is just a piece of grilled fish and a sweating beer away. (http://www.lonelyplanet.com/cameroon#ixzz3XkFKoydd)
Cameroon has a tropical climate with abundant rainfall to the south and it gets drier as one goes north. Coastal areas get an average of 4060mm of rain. The exposed slopes of Mt Cameroon get constant rainfall (sometimes 10,160mm) making it one of the wettest regions of the world. Cameroon has its rainy season from July to October and it gets hot and dry between November and March. Temperatures vary between the north and south. The central grasslands are cooler compared to the rest of the country because of regular rainfall. March is usually the hottest month and September and October the coolest. The four seasons are not very distinctly marked.