The best time to visit Guatemala is from early November to mid-May, which is the dry season. It is very difficult to get around the remote areas during the rainy season. The week leading up to Easter sees elaborate ceremonies which are a highlight of the calendar, particularly around the town of Antigua. March and April are very hot and sticky in the low-lying areas along the Pacific coastal plain, so plan your trip with all these factors in mind. It may be cold at night at higher altitudes, and frost may be possible. You will need a good suntan lotion for daytime, and insect repellant is a must. Wear a broad brimmed hat and sunglasses for protection, as the sun can be strong even in the highlands. Altitude sickness is possible for the hiker, especially above 4000 meters. Always sleep under a mosquito net in the wet season. This will also protect you from being bitten by vampire bats, which must be reported. You should get tetanus and rabies shots immediately.