Temperatures for the past two days (July 12th and 13th) have been in the 90s- Thursday (July 12th) we hit 91, and Friday’s (July 13th) high was 92. If today’s high (July 14th) hits 90 or greater (the forecast is for the low 90s), we will have our third heat wave of the summer. A heat wave is when temperatures reach 90 or greater for three or more consecutive days.
On an interesting note, yesterday was the 4th Friday of the summer where temperatures reached 90 degrees or warmer.
Last year we only had one heat wave- for the WHOLE summer! Today we could be looking at our 3rd this summer!
So what’s causing these heat waves?
Heat waves occur when a warm air mass stays over an area for an extended time. Warm air masses that cause heat waves are usually associated with high pressure systems. However, sometimes hot air ahead of low pressure systems can keep things hot for long enough to cause a heat wave. We are currently experiencing abnormally dry weather (one step up from a drought), partly because of the frequent high pressure systems in the area. High pressure is associated with dry conditions, whereas low pressure systems tend to bring precipitation (in the summer, this is in the form of rain). These pressure systems, or air masses, often move through a region over the course of a day or more. This is because it is “pushed” out of the way by another air mass. But if there is nothing in the area to push it out of the way, the air mass will stay over a place for several days, which can result in unsettled weather if it is a low pressure system, or sunny weather if it is a high pressure system.
So what’s up with 4 Friday’s in a row of 90 degrees this summer?
Well, one of the reasons meteorologists can forecast the weather is because weather tends to follow a pattern. Because of this, meteorologists can look at what the weather is like in another part of the country and predict when it will reach their location. Sometimes you may notice that for a few weeks, it always seems to rain on the same day of the week, and eventually that changes. Well, in the pattern we are seeing right now, the hot weather tends to be towards the end of the week and into the weekend, which is why Fridays lately have been in the 90s.
Weather can be difficult to predict, because there is much more that influences it, but knowing the patterns can give you a fairly good idea of what is to come.
-Eileen Carmody, weather intern