Extreme negative response to heat

This sounds super serious. I just recently bought into heart rate training because I too struggle in the summer months. Realized I was training significantly harder than I should have these last two years. Still had tremendous PR’s. Anyways.... are you using your watch or a chest strap monitor? Watches are extremely inaccurate compared to chest straps which is 99%+ accurate.

Run first thing in the morning. I don't know where you live, but in most parts of the country it's usually below 80 degrees just before sunrise. I currently live in inland central California where the highs are often over 100 but the humidity is low and the lows usually dip below 70. I start my runs around 5 am when the sun hasn't risen yet and the temperatures are usually quite tolerable. I lived for four years in Kansas where the lows were often closer to 80 with much higher humidity, but even there it was marginally tolerable before and shortly after sunrise in the morning.

I hate hot weather too and I don't think it's wise to beat your body up by running in the heat.

At first I just had a watch, and figured it was inaccurate. I got a chest strap, but didn't see any major changes. I hate the chest strap and went back to just using the watch because they are showing the same readings. If I feel like it's way off, I'll stop my run and take my heartrate manually, but the watch has always been spot on.

I live on a subtropical island, so humidity is ridiculously high in the morning during summer. Temps are a little cooler and I'm not in the sun the whole time so this is probably my best option. I have a job that doesn't have set hours so I can't run at the same time every single day, which is another challenge.

I'm really considering just running on the treadmill everyday. I have always hated the treadmill but I don't want to spend 4 months suffering without improvement.