Weather conditions are an important driver of demand for electricity. Very warm days during the summer season are associated with peak electricity consumption. As California has moved toward a zero-carbon, high-renewables electricity system, the need for improved weather data and information has increased. Hourly weather data are highly variable (“noisy”), with frequent observational errors and instrumentation failures, making data use difficult. In this project, the research team designed and implemented a series of tests to produce a stable record of hourly weather data for use by the energy sector. After careful data quality review, the team produced a curated repository of hourly weather observations at 39 locations across California for 1973–2019. This report discusses the utility of this product and provides recommendations for how best to use the data and supporting documentation. California’s warming trend is asymmetrical — stronger in the late afternoon and weaker shortly after sunrise. The report discusses regional and seasonal differences from the statewide trend, with a focus on implications for California’s electricity supply and demand. Data products used in this work form the basis for the development of a statewide, multilevel subdaily repository and represent a clear pathway forward to providing energy sector stakeholders with regular ultra-high-resolution data products that are critically needed to help California meet its renewable energy and climate goals. Last, the report quantifies the value of Pacific Ocean surface conditions in informing predictions of temperature in California and outlines an approach for making such predictions operational. The data produced and analyses performed in this project provide investor-owned utilities as well as public utilities and state agencies with insights into the effects of subdaily weather on the electrical system.
