“What can be the cause of vaginal itching?”

This could be irritation from soaps, detergents, contraceptive barriers, menstrual care products, vaginal gels/lubricants, semen, urine or feces following wiping, or clothing material or clothing fit/tightness. Sweating may also cause some irritation if the symptoms occur after strenuous activity. Dryness of the area such as that due to low-estrogen conditions (premature menopause or certain medications) are possible. Yeast infections and sexually transmitted infections could cause itching. Some patients can experience changes of the vulvar skin due to immune-related conditions as well.
For 2 weeks I advise avoidance of: scented detergent (use baby-friendly detergent) and dryer sheets, tight fitting underwear (don’t wear any underwear at night), tight pants/pantyhose/leggings, soaps to the vulva, vulvar fragrances, sexual intercourse and douching, scented toilet paper, and aggressive wiping of area after toilet use.
If the symptoms persist you should see your gynecologist for an exam.

Many possibilities but most likely a common yeast infection especially in summer months when you tend to perspirere alot. Try an over the counter cream like monistat and if it doesn't work then see a gynecologist for some testing and an examination.