In terms of precipitation, rainfall in Jember ranges from 1.7 - 17.0 inches per month. January is typically the wettest month, when rainfall can reach 17.0 in. August is typically the driest time to visit Jember when rainfall is around 1.7 in.
If weather is an important factor for your trip to Jember, use this chart to help with planning. For those seeking warmer temperatures, October is the ideal time of year to visit, when temperatures reach an average of 78.8 F. Travelers looking to avoid the cold should look outside of July, when temperatures are typically at their lowest (around 75.2 F).