To convert -15 degrees Fahrenheit to Celsius, we can use the formula:

°C = (°F - 32) * 5/9

Plugging in the value, we get:

°C = (-15 - 32) * 5/9

°C = (-47) * 5/9

°C = -23.888888...

Rounding to two decimal places, the temperature in Celsius is approximately -23.89 degrees Celsius.