What do I wear for a volunteer orientation??? Someone please help😩😩😩

Yo

I have a volunteer orientation on Wednesday at an organization that distributes food to low income people/families. This will be their first time seeing me because the position did not require an interview. I want to appear professional, but I know that there is a bit of physical activity involved and that I may have to be outside in 90 degree weather. I have no clue what to wear. Please help!