Unexplained weight gain

I've been tracking on MFP for almost a year. Maybe 2-3 months ago I started getting a bit lazy with tracking. I still tracked but took bites here and there, tracked at the end of the day instead of as I ate, etc. I noticed that the scale started to creep up (I went from 110 to 112 to 114...). This made little sense since it coincided with a period where I was eating less but a few weeks ago I adjusted my goal from maintain to lose .5 lb a week. Since then I've been logging religiously again.

Previously, I had been following my fitbit as a guide and eating most of my exercise calories back (per fitbit). I still had a deficit every week ranging from 500-1000 calories.

I weighed for the first time today since starting my deficit again and I'm still 114. I'm flummoxed! I've been eating at a deficit for about 3 weeks. A few months ago I was eating 2000+ calories per day (per my fitbits guide) and easily maintaining at 110. Now I'm logging under 1500 most days and not losing. At this point I'm fine with staying where I am weight wise but I certainly don't want to gain any more.

Is there any chance that weather is contributing to this? It's hot and humid here and I do spend a lot of time outside.

My diary is open if any one has insight to share.