Tomatoes, squash and beans grow here in abundance. We recommend that you bring light clothing for day use and a sweater for the evenings when it's a bit cooler. That was it. They had more on laundry than on the climate. T here is a magazine called Destination Guatemala that is usually pretty good.
Weather conditions vary from season to season and region to region.
Not much help there. The dry season is from October to early May and the rainy from late May until the end of September. Fine as long as you don't leave Guatemala City, Antigua, Chichicastenango or Atitlan. T he truth of the matter is that no one thinks about the weather much because you don't have to think about it. Chicago it's not.