Accurate estimates of pedestrian volume are important for analyzing pedestrian movement and safety; methods to estimate these volumes are continuously evolving and being improved. However, relatively little is known about the impact of weather conditions on pedestrian activity. This paper evaluates the effect of weather by including temperature, cloud cover, wind, and precipitation variables in a linear regression model of pedestrian volumes. Pedestrian volumes were collected over approximately one year using automated counters at 13 different locations in Alameda County, California. These volumes were compared with weather data available from nearby weather stations. Results show that several weather variables had a significant influence on pedestrian volumes during certain time periods. Rain had the largest effect on pedestrian volumes at a given location, though clouds, wind, and both hot and cold temperatures were also shown to decrease volumes. This study demonstrates the importance of accounting for weather when analyzing pedestrian volumes. Future research should attempt to understand how the effect of weather conditions on pedestrian volumes varies by geographic region, time period, and local land use and site characteristics.