Lots of problems can cause hematuria like polyps in the urinary tract (mainly the bladder), stones, infections and large prostate.
In general, a urine test and an imaging of the urinary system must be done along with a cystoscopy, unless another very obvious cause if found.
1)Dehydration and poor water intake forces the kidneys to concentrate urine in order to preserve water, resulting in dark urine. during summer season, we tend to loose big amount of body water and thus 2L of water might not be enough to keep the nody well hydrated
2) Certain foods could result in red-colored urine, such as beets
4) Certain medications could change the color of urine, or even result in hematuria, such as rifampin and anti-coagulants
5) Urinary stone disease can lead to hematuria
6) Urinary tract infections may present with hematuria
7) Bladder tumors could present with hematuria, though it is very very rare in your age group
8) Hematuria could be due to kidney parynchemal diseases, in which RBC morphology (shape) would be altered
First thing to do would be to do a urine analysis test with RBC morphology, as well as creatinine in blood, and then visit your urologist for further testing and treatment if needed.