Given the different temperatures that you are likely to encounter, layers are essential. Take a selection of t-shirts, a thin microfleece layer for cooler evenings, and a water- and wind-proof jacket.
You can use the jacket in different situations, whether it’s to protect against the cold when climbing a volcano or staying dry in a sudden downpour in the jungle.
Make sure you take a pair of shoes that are good for walking if you want to go hiking, or at least a pair of trainers with decent grip. You don’t need to take top-of-the-range technical gear, but your feet will thank you if you make an effort. Even the cobblestones of Antigua are uncomfortable if you’re knocking around in a pair of Converse.
Another good tip is to take a pair of trousers, even in the hotter months. Locals rarely wear shorts and you’ll stick out like a sore thumb if you wear them all the time. Especially in Guatemala City it’s a good idea to wear trousers to avoid undue attention.
Health products tend to be expensive in Guatemala, so take as much sunblock, insect repellent and other stuff as you can. In certain places it can be difficult to get hold of some products, so stocking up is wise.
Street crime can be a problem in Guatemala, so it’s best to leave jewellery and other valuables at home. Take your camera if you’re a keen photographer, but be careful not to walk around with it on display. Anything that might attract the wrong kind of attention is best kept out of sight.