Hi Kate
Sorry to hear your baby is suffering at the moment. Green poo can be absolutely normal so don't orry too much right now.
How often is she pooing? Is it runny or hard or does it smell bad? Is she feeding OK? (Breast or bottle?)
Sometimes babies have a one-off crying day that feels like it's never going to stop. if she hasn't really had a problem until now, she might be going through a growth spurt and be more hungry or just finding it hard to settle in the heat.
Did you notice anyting in particular that helped her stop crying at times?
Try to leave her as undressed as possible but out of the sun, in this weather, as she may be feeling hot, damp or too enclosed in her outfit. Sometimes just stripping a baby off and letting them lay down on a towel (in case of wee or more green poo!) can help them to relax if they get into a cycle of tears and frustration.
How is the poo today? Some babies, epsecially breastfed babies, don't poo every day, but do keep an eye on how it changes.
Your babies stomach is still very young hence the changes in 'stool' appearance! But also, don't feel afraid to mention it to your GP if you are very worried.