Lake tahoe: Weather Forecast. The warmest day over the next 7 days in Lake tahoe is forecast to be 2nd September at 34°C (93°F) and the warmest night on 2nd September at 15°C (59°F). The average temperature over the next 7 days is forecast to be 33°C (91°F) . The average for August is 0°C (0°F) in Lake tahoe. 1  Fri 1 Sep 33°C (91°F) E 7mph. (11kmh) Night 13°C. 2  Sat 2 Sep 34°C (93°F) NE 6mph. (10kmh) Night 15°C. 3  Sun 3 Sep 34°C (93°F) SW 6mph. (10kmh) Night 14°C. 4  Mon 4 Sep 34°C (93°F) W 7mph. (11kmh) Night 14°C. 5  Tue 5 Sep 33°C (91°F) N 8mph. (12kmh) Night 15°C. 6  Wed 6 Sep 34°C (93°F) WSW 5mph.