Averages for Kathmandu in June. June is hot and muggy in Kathmandu. The day time temperature can even reach up to 40°C. The end of June also marks the beginning of the rainy season. Nepal receives quite a lot of rain, which could even be described as relentless. Nepal receives 80% of its rain from June to September. The average daytime temperatures are around 27°C (81°F) whereas the average minimum temperatures are around 6°C (43°C).