Some 15 people have lost their lives so far in Uttarakhand and at least 10 were reported dead in the remote Arunachal Pradesh state.
"We have recovered 15 bodies so far. The rescue operations are on to find those still missing," senior disaster control officer in Uttarakhand , Piyoosh Rautela, told AFP.
Television images showed muddy, swirling floodwaters gushing through the area, while giant boulders and rocks blocked part of a national highway.
In Arunachal, a nine-month old baby and a 10-year-old were among those killed after debris barrelled down hilly slopes into populated areas, the Press Trust of India news agency said, quoting police.