No it's not, brother!
High temperatures drastically decrease lithium-ion batteries' life expectancy. It's just chemistry! Exposure to high temperature is pretty much the worst thing you can to your battery.
If you're going to stay in Africa for an extended period, say a whole year or two, then you may want to either replace the battery or buy a new phone.
A lithium-ion battery can maintain a maximum of 60% of its total capacity for at most 4 years under "ideal" conditions. Needless to say; Pakistan's hot climate is less than ideal for lithium ion batteries and that HTC 10 of yours is already 3 years old so...
Well, I think I've made everything crystal clear!