ForecastWatch, a company solely dedicated to analyzing the accuracy of weather forecasts, has a good study available: https://www.forecastwatch.com/wp-content/u

ForecastWatch, a company solely dedicated to analyzing the accuracy of weather forecasts, has a good study available: https://www.forecastwatch.com/wp-content/uploads/High_Temperature_Accuracy_Study_12_Years.pdf https://www.forecastwatch.com/wp-content/uploads/High_Temper... You can also check accuracy for your local zip code (in US) at: https://www.forecastadvisor.com/ https://www.forecastadvisor.com/ tldr: for the best US consumer weather forecasters the mean error on high/low temp for 1-5 day forecasts is around 3F and they hit within 3F within 70% of the time. 7-day has declining accuracy and 10-day is not much better than statistical analysis on historical trends.