Typically, the average weather in Cupertino during the month of September is 19 with usual highs being around 27 and low being around 14 celsius. The table below includes more detail:
| Month | Degrees Celsius |
|---|---|
| Temperature | 19 |
| High Temperature | 27 |
| Low Temperature | 14 |
Useful Links: Cupertino Weather: Average Weather & Yearly Climate