AIBU to tell work I won't go to this event tomorrow?

[Waggamamma]

My colleague has arranged for my work to hold an information stall at a public awareness event tomorrow. My colleague can't actually make the event as she has another meeting. I have to do 9am-1:30pm and another colleague in the afternoon. Its in a marquee in the middle of town.

Thing is it's currently 2 degrees here and an inch of snow on the ground (still snowing!). It will be freezing tomorrow, sat in a marquee all morning! I don't cope well in the cold.
I'm also ten weeks pregnant and still being sick 4-6 times a day and worried about lack of toilets/not making it on time and vomiting in public. Nobody at work knows I'm pg except my manager.

AIBU to say I won't attend the event? it will leave everyone in the lurch as I know there's no one cover it and it will look bad on the organisation who invited us along if we don't go.

I never considered risk assessment mini I guess it's not really lone working though as there are other people there from other organisations. I'm not sure if being cold is anymore of a risk to pregnant people than it is to others?

I just need to get on with it and wrap up . I'm not coping very well with this pregnancy and I just know an event like this is going to leave me puking and exhausted for the rest of the week. I asked my midwife if it was normal to feel like this, she said it is .

Actually I'd say it is lone working. There's no guarantee the other people nearby won't disappear, and they certainly have no obligation to help you. It's tantamount to a risk assessment saying "it'll be fine, we rely on the kindness of strangers".