Spiti is best in every season. it's depend on you what do u want to experience.. for snow capped mountains try winter expedition otherwise visit in July or August..
March to June is the perfect time to visit Spiti. During this season, when the temperature ranges from 0-15 degrees Celsius, which starts from March and lasts until June, those who are on a relaxing vacation can visit Spiti. The winters at Spiti are for the courageous.