Thing is when you're hot you will burn more calories than normal because your body is working hard to cool down. So it's probably accurate but as editorgrrl said the only way to know is to just trust it and see what happens.

It is not accurate. You can not trust it.

While the heart is beating faster to aid in blood cooling - the increased HR and calorie burned from just that heart muscle going faster is no where near what the formula thinks as a result of inflated HR.

This is exactly one of several reasons why HR-based calorie burn can be easily thrown off - increased HR not based on an actual increase in effort.

Same effect when dehydrated, thicker blood, heart must pump more and harder to get the same amount of oxygen around, but not because you are working harder and burning more calories, except for a few more by the heart beating faster.

Or getting scared or nervous, HR is up from adrenaline and fight or flight response preparing, but no actual increase in workload yet. When you fight or flight, sure, but even then, probably inflated.

I would not frankly wait 4 weeks to find out if you keep up that daily type of routine - you'll get fat overeating, because that sounds high enough you'd be not only going over eating goal but wiping out deficit and going over maintenance too.

I've been waiting for these types of responses - which means you are the first one to notice the increased calorie burn and HR and wonder about it, out loud.
Pretty sure there are tons of others out there getting exactly the same inflated HR either from heat or dehydration that haven't noticed yet, or just think they are working harder, perhaps not noticing the pace or speed is exactly what it's always been.