Accurate estimation of in-situ concrete compressive strength is vital for structural safety and optimizing construction schedules. However, significant discrepancies often exist between standard laboratory-cured specimens and actual field performance due to varying on-site temperature and curing conditions. This study proposes a practical approach to bridge this gap by employing the maturity method to derive a site-specific strength modification factor (SMF). The proposed method was rigorously validated using extensive data collected from five active construction sites in southern Iran, which encompassed a wide range of concrete mix designs and local climatic conditions. A total of twelve experimental series were conducted, directly comparing the compressive strength development of standard laboratory-cured specimens with companion field-cured samples at 7 and 28 days of age.The results establish a significant and quantifiable correlation between the calculated SMF and the ambient curing temperature. Specifically, the SMF at 7 days averaged 1.30 during colder seasons, indicating lower early strength in the field, and 0.86 during warmer seasons. By applying this temperature-dependent SMF to standard laboratory results, the mean prediction error for in-situ strength was substantially reduced from approximately 14% to less than 4%. These findings demonstrate that the SMF approach provides a reliable, quantitatively robust framework for adjusting controlled laboratory data to accurately reflect real-world curing environments. Consequently, this method offers a powerful tool for enhancing on-site quality control protocols and enabling safer, more efficient, and data-driven decisions regarding formwork removal and subsequent construction activities.