A new drought index, the Standardized Precipitation Evapotranspiration Index (SPEI), is proposed, which combines precipitation and temperature data to assess drought severity. The SPEI is based on a water balance and accounts for the effects of temperature variability, making it more sensitive to drought conditions than the Standardized Precipitation Index (SPI). Unlike the SPI, which only considers precipitation, the SPEI incorporates evapotranspiration (PET), allowing it to capture the impact of temperature on drought severity. The SPEI is also multiscalar, enabling it to detect droughts at different time scales, which is crucial for drought monitoring and analysis. The study compares the SPEI with the self-calibrated Palmer Drought Severity Index (sc-PDSI) and SPI across observatories with varying climates. Under global warming conditions, the SPEI and sc-PDSI both show increased drought severity due to higher water demand from evapotranspiration. The SPEI's multiscalar nature makes it more suitable for monitoring different drought types and assessing their impact on various water sources. The study also demonstrates that the SPEI can account for temperature variability and extreme events, such as the 2003 European drought, which the SPI cannot. The SPEI is simpler to calculate, requires fewer data, and is more effective in capturing the effects of global warming on drought conditions. The results show that the SPEI provides a more accurate representation of drought severity under changing climate conditions compared to the SPI and sc-PDSI. The study concludes that the SPEI is a more suitable drought index for future climate scenarios due to its multiscalar nature, ability to account for temperature effects, and lower data requirements.A new drought index, the Standardized Precipitation Evapotranspiration Index (SPEI), is proposed, which combines precipitation and temperature data to assess drought severity. The SPEI is based on a water balance and accounts for the effects of temperature variability, making it more sensitive to drought conditions than the Standardized Precipitation Index (SPI). Unlike the SPI, which only considers precipitation, the SPEI incorporates evapotranspiration (PET), allowing it to capture the impact of temperature on drought severity. The SPEI is also multiscalar, enabling it to detect droughts at different time scales, which is crucial for drought monitoring and analysis. The study compares the SPEI with the self-calibrated Palmer Drought Severity Index (sc-PDSI) and SPI across observatories with varying climates. Under global warming conditions, the SPEI and sc-PDSI both show increased drought severity due to higher water demand from evapotranspiration. The SPEI's multiscalar nature makes it more suitable for monitoring different drought types and assessing their impact on various water sources. The study also demonstrates that the SPEI can account for temperature variability and extreme events, such as the 2003 European drought, which the SPI cannot. The SPEI is simpler to calculate, requires fewer data, and is more effective in capturing the effects of global warming on drought conditions. The results show that the SPEI provides a more accurate representation of drought severity under changing climate conditions compared to the SPI and sc-PDSI. The study concludes that the SPEI is a more suitable drought index for future climate scenarios due to its multiscalar nature, ability to account for temperature effects, and lower data requirements.