We went in the middle of May, which is before it gets very hot in Njivice.
It was comfortable or hot during the day and cool or cold at night. That would have been ideal except we could not get the air conditioning unit to work, which made it a little uncomfortably cold first thing in the morning in the cabin. Not a big deal really.
There was a TV in the room but had only 3 channels, 2 german ones and a horrific US one playing some weird bible bashing creep.
Ok, so we don't mind the cold too much and are not interested in TV anyway. We paid £3 per day for a resonable internet connection and that was great as we could listen to the BBC radio and play Netflix as much as we wanted.
The resort was really nice. A string of nice restaurants along the boardwalk. Very good food, good service and excellent Croatian wines - merlot, cab sav, etc. And cheap. The beers and wines were about 75% the prices in the UK. Eating out was about 50% the prices in the UK, and just as good for choice and quality. No english beers at all though, which is unusual these days for an EC country, but there were good lagers and one or two decent dark beers.
We were on an island abuot 20 miles long with about a dozen towns and we spent the entire holiday driving from one to another. Spotlessly clean everywhere. An excellent road system with very little traffic. Some interesting architecture, very different from northern EC countries. Friendly enough people, but hardly anyone spoke english or french, although I suspect that german would be covered better.
This was our second holiday in Croatia and we would definitely be happy to go again. If you have never been be warned that in the shallows off many beaches there are black urchins which have fragile and razor sharp spines. The slightest touch results in a batch of spiny splinters. You must either wear shoes, costing £5 a pair, or make sure you go in and out of the water from concrete jetties, which are very common. In May the Adriatic was too cold for swimming, so we didn't encounter any problems with the urchins.
Overall, had a very relaxing and good value for money break and would happily do that in May or September any year.