In the Pantanal, the rainy season runs from December to March, with more than 70 percent of the total rainfall occurring at this time. The rains are intense, flooding the Pantanal, and temperatures are high.
The dry season (July to September) or the intermediary seasons (April–June and October–November) are the best times to visit this area. The average daytime temperature in the Pantanal this time of year is around 90ºF, but mornings and evenings can be quite chilly in June, July, and sometimes August, with temperatures dipping to near 40ºF.
Keep in mind it can be both hot and very cool, and rain is always a possibility. Thus, you should be well prepared for any type of weather conditions. Again, although temperatures during the day will be quite warm, you will probably want to wear long pants and a jacket in the evenings if you are traveling in June or July.