Your blood pressure changes constantly. First off, there are correct ways to take your blood pressure. You should be in complete rest for 5 minutes before you take it, ie do not take it after you work out! If it is extremely hot out, by your standards, your blood pressure will be high, because you are already stressed! So do not take your blood pressure if your body is hot from being outside in the heat all day! I would guess that in the winter, if cold enough, by your standards, this would also increase your BP, due to the stress.
I have high blood pressure, if I do not take my meds, it will not be long before I am 140 over 100 or higher on both scales! When I was first diagnosed, I was prescribed meds, they worked, kept my bp down to acceptable levels, one day I forgot my morning meds, by 10 am, through the roof! Had to go home to get them!
Your bp is not constant, its a daily average, 120 over 80, is the acceptable limit. Some times you might be 110 over 70 , 105 over 85, up and down like a yoyo! As long as it stays under the ceiling 120/80 its all good!
IF YOU HAVE CONCERNS ABOUT YOUR BP,SEE YOUR DOCTOR!! This is not something to fuck with!