Objective: Alternating current (AC) series fault arcs pose significant fire hazards in residential and industrial settings because of their high energy density and ability to ignite combustible materials. Environmental factors, such as ambient temperature and relative humidity, influence the initiation, development, and energy release of fault arcs. Existing studies have primarily utilized simplified experimental conditions or qualitative observations, providing limited quantitative evidence on the effects of ambient temperature and relative humidity on arc characteristics. This study aims to systematically quantify the effects of ambient temperature and relative humidity on the electrical characteristics and energy release of AC series fault arcs. Methods: A multiparameter fault arc experimental platform was built by combining a temperature-and humidity-controlled chamber with high-precision electrical signal acquisition instruments. The setup included an AC power supply, a 40 Ω resistive load, voltage and current probes, an oscilloscope, and a manual electrode separation mechanism. Series fault arcs were generated between a copper cone electrode and a fixed carbon electrode under controlled separation conditions. Two series of experiments were conducted: (1) In one series, the ambient temperature varied from 5 to 30 ℃ at 45% relative humidity, (2) while in the other, the relative humidity varied from 20% to 80% at 25 ℃. For each condition, multiple repetitions of the experiment were performed to ensure statistical reliability. Electrical signals were recorded and then processed by a discrete wavelet transform to remove noise while preserving the transient characteristics. The root mean square (RMS) values of current and voltage, as well as the instantaneous power integrals, were calculated to quantify the electrical characteristics and energy release. Results: The results revealed that RMS current generally increased from 4.64 A to 4.85 A as the ambient temperature increased from 5 to 30 ℃, indicating enhanced ionization and reduced gas density in the arc channel; meanwhile, the RMS voltage decreased from 30.55 V to 21.68 V, indicating lower arc impedance at higher temperatures. Increasing the relative humidity caused slight reductions in RMS voltage and energy release, while the RMS current remained largely stable, suggesting that higher humidity suppresses arc stability through enhanced cooling and electron recombination. These findings indicate that ambient temperature has a dominant influence on arc current, whereas voltage and energy release are moderately or weakly affected by environmental factors. Conclusions: This study establishes a robust experimental and analytical framework to quantify the impact of ambient temperature and relative humidity on AC series fault arcs. The results demonstrate that the electrical characteristics and energy release of fault arcs are sensitive to environmental parameters and exhibit nonlinear and condition-specific responses. These findings provide quantitative evidence for understanding the mechanisms underlying fault arc behavior and highlight the importance of considering environmental factors in fire risk assessments. The framework can support the development of tailored arc-fault mitigation strategies and improve the design of electrical systems to reduce fire hazards across diverse residential and industrial environments.