Social media activity can be used to examine exposure to heat waves in US cities, based on a study at Florida State University. Although a variety of weather metrics have been used in association with health outcomes, such heat exposure metrics do not account for distance from weather station, the effects of ventilation and air conditioning, and other individual conditions (e.g. clothing, health status). Researchers evaluated over 230,000 tweets from 2,216 US cities mentioning heat, air conditioning, electrical outage, and dehydration, for 182 warm-season days in 2014. A positive association between outdoor maximum temperature and tweet counts for most major cities was observed, among others, but the quantitative relationship varies for different cities. The first heat wave of the year, which is typically associated with greater health impacts, is especially well captured by tweeting activity. Despite their representativeness limitations, these results may help local public health authorities complement extreme heat warning systems, particularly where no heat syndromic surveillance is maintained.