Gaining weight after exercise?

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Hi there,
Does anyone weigh in MORE the next day or few days after an intense workout? I did 11.6 miles run/walk on Friday and over the weekend my weight went up a good 6-7 lbs. It still is much higher than "normal." Assuming it's not my time of the month and I am adequately hydrated, what could possible causes be? I don't attribute it to muscle gain.... thoughts?
Thanks!