SPRING and AUTUMN are best seasons in Nepal if you are planning for Himalaya trekking, but for tour all seasons are best.
WINTER December - February = This season is noted for occasional snowfall only at higher elevations. This season is ideal for trekking at lower elevation, generally below 4000m
SPRING March - May = This is the one of the other best times for any offering different varieties of wild flowers, specially the rhododendrons
SMMER - MONSOON June - August = Summer months continue up to mid September making travel wet and warm. higher valleys and meadows blossom with flowers and lush
AUTUMN September - November = This season is considered the best time for trekking in Nepal, which offers excellent weather and tantalizing mountain views. Temperatures are modeone.The skies are generally clear.