Gaining weight in summer

Becoming concerned. This past week my weight is on an uphill climb.

I’m already quite slim and watch what I eat/weigh.

Nothing has changed. In fact when I saw it going up, I tried to decrease my intake a little and it seems to have plateaued....

My question is, could it be I’m retaining a bunch of water? Does the heat make you absorb more?

I tried drinking more water to flush whatever is in there but it doesn’t seem to be doing much.