Exposure to environmental factors such as high temperatures and solar radiation levels present a welfare concern for many domestic equids. Understanding how these factors influence the shelter use of healthy equids can inform welfare guidelines. While there is research assessing horses’ responses to hot, dry climates, the use of shelter by healthy, semi-free ranging donkeys and mules has not been assessed. We observed the shelter seeking behaviour (SSB) of 109 donkeys and 21 mules, with free access to constructed shelters, across two locations during summer in Southern Spain. The location of each equid, either utilising a constructed shelter, outside unprotected or using natural protection, was observed. This was recorded alongside measures of environmental conditions including temperature, lux, wind speed and level of insect harassment. Equids were observed using some form of protection from the elements in 39% of observations. Increasing temperatures and lux levels predicted increased shelter use whereas temperature and wind speed were key predictors of outside protection use. Compared to donkeys, shelter seeking by mules was more sensitive to changes in a number of environmental factors including lux, temperature and level of insect harassment. Results indicate that rates of protection use are quite high in these conditions and that shelters are utilised under particular environmental conditions: high temperatures, high lux levels and increased wind speeds, indicating they are likely to confer a significant welfare advantage.