Based on the context and the answer, generate a question. 

Context: Today we rode our bikes along the river with our friends . We ate orange duck crackers while sitting on that concrete slab and then continued down the trail to this little beach . The water was pretty cold , though not quite as cold as it was the last time we visited .

Answer:

It was past summer and cooler weather had set in .



What may have been the reason the water was cold ?