How long will it take a letter mailed from San Diego to Philadelphia PA?

The delivery time for a letter mailed from San Diego to Philadelphia typically takes about 3 to 5 business days using standard USPS First-Class Mail. Factors such as weather, holidays, and mailing volume can affect delivery times. For faster service, options like Priority Mail can reduce the time to 1-3 business days. Always check with the postal service for the most accurate estimates.