Shampooing frequency per day

How many times a day do you shampoo?

I used to wash my hair only once in the morning before going out, but

In the summer, when I come back from going out, it's so hot that I sometimes take a shower right away and shampoo again while I'm at it.

I heard that removing dirt in the evening after going out is good for the scalp, so I think washing my hair in the evening might be a good idea.

Then my hair gets a mess in the morning and I have to wash it again.

I'm not sure if shampooing more than twice a day irritates the scalp and hair or if it might actually be worse.