Definitely call your ob as it could be blood pressure related.
That definitely sounds like high blood pressure, please go get it checked just to be safe! I've had to deal with high blood pressure issues and preclampsia scares for 7 weeks and the first signs are headache and blurried vision.
I agree with Amy, definitely call your OB, make sure you're drinking LOTSS of water, like gallons haha! Good luck!
Could be high blood pressure. Or, if it's really hot you may be experiencing heat stroke. Make sure you're well hydrated get some rest and if it doesn't go away soon, I would call your OB