There are some fading showers out there this morning and the sun will be returning shortly and we’ll start to heat back up again. Yesterday we topped off at 96° officially at KCI…some areas were a notch or two hotter. That bright sunshine in the afternoon really did the dirty work to getting us hot again.

We continue to watch the data over the coming days…while hot…nothing too crazy out there in terms of heat. We’re coming into the hottest time of the year, starting this weekend and continuing into the 1st week of August…so it’s supposed to be hot.

The issue is do we cross the threshold of it being a “heat wave”. This is a fascinating term to me. Did you know that in many areas of the world there is NO common definition for a heat wave. For example…what is a heat wave in KC?



Today: Clearing out and hot with highs in the mid 90s

Tonight: Partly cloudy and warm with lows in the low to mid 70s

Tomorrow: Partly cloudy and hot again with highs in the low to mid 90s. Late day showers/storms into the evening are possible. Coverage may not be all that great though

Sunday: Clearing out and perhaps not as hot with highs closer to 90°



So back to the original question…what is a heat wave? What is the criteria for a heat wave? According to the Encyclopedia Britannica…

“No formal, standardized definition of a heat wave exists. The World Meteorological Organization defines it as five or more consecutive days during which the daily maximum temperature surpasses the average maximum temperature by 5 °C (9 °F) or more. Some countries have adopted their own standards. For example, the India Meteorological Department requires that temperatures increase 5–6 °C (9–10.8 °F) or more above the normal temperature, whereas the U.S. National Weather Service defines a heat wave as a spell of “abnormally and uncomfortably hot and unusually humid weather” spanning two days or more.”

I’m sort of interested in the last sentence.

According to their website…

“A period of abnormally and uncomfortably hot and unusually humid weather. Typically a heat wave lasts two or more days.”

They didn’t have a time period criteria.

NOAA says this…

“A heat wave is a period of unusually hot weather that typically lasts two or more days. To be considered a heat wave, the temperatures have to be outside the historical averages for a given area.”

So really there is no SPECIFIC definition of a heat wave…and certainly not for KC! Some feel that it is 3 straight days of highs 95°+. Again though…this is just a subjective definition. There isn’t a real definition that I can find. IF you can find one…let me know.

What about this scenario…temperatures near 90° with high dew points…let’s say close to 80°. Your heat index would be close to 110°! Let’s say you do that 3 days is a row…is that a heat wave? Compare that to highs of 95° with dry air…dew points in the 60° (sort of like what we’ve seen this week). Your heat index would be right at 95°. Which is worse?

I just find this fascinating. It’s semantics…but important semantics. Our average high is now maxing out at 89°…so IF you go simply by the 95° baseline…that means that a heat wave here…would be a period of consecutive days with days 6° above average…which sure doesn’t seem like much in the dead of summer.

Anyway food for thought.

Let’s go with the simple version though I guess…3 straight days with highs 95°+.

So far this year we haven’t had a “heat wave”. This could change after today and tomorrow…maybe.

This could change later next week though…and those chances are increasing.

Now about that.

We’ve been very fortunate that we’ve missed out on the worst of the extreme summer heat for awhile. Last year we topped off at 98°…which we did 5 times. The year before that we hit 94° which is crazy for a summer in KC…no heat waves obviously.

As a matter of fact here are all the 100°+ days going back to 2010

The often cited stat of the last 100°+ day in KC being in 2018 is glaring. Before that we have to go back to 2012! That was the year of a nasty drought around these parts. It was brutally hot but we had so little soil moisture that the dew points weren’t all that bad at all…very reminiscent of what happens in the desert actually.

So the last time we were above 100 was 2012.

Why am I bringing this all up?

Well depending on how things play out later next week…with a building heat dome into the Plains…and the significant heat that has been sitting in Texas/OK for weeks…it’s conceivable that the temperatures here can really go up. The lack of soil moisture has certainly played a role in parts of the Metro exceeding 100, mainly on the south side already this season.

The north side though hasn’t gotten there yet. The hottest so far has been 97° back in June at KCI…and KCI is the “official” station for KC (for right or wrong). Olathe Executive has hit 101°.

So it’s possible…assuming we keep losing our soil moisture and it’s not replenished by heavy rains in the next couple of days…that we are setting up for 100°+ degree weather. This potentially is a nasty heat dome coming into the Plains. It’s why yesterday I sent this tweet out.

It may sound like hyperbole BUT remember we only need to get to 101° at KCI for this to be true! 101°…that’s it.

Heck we could do that on Tuesday ahead of a weak front coming into the region…then the higher chances may be starting next Friday into next weekend.

It would require the right set-up of minor to no rains in the days leading up to the potential. Dew points that aren’t extremely excessive…and no “ridge runner” disturbances that can create clouds and scattered showers/storms like this morning. Model data is pretty bullish on the heat. The GFS data has been biased as way to warm (model errors) not only here but around the world. The EURO data though is sniffing this potential out too…and it’s reasonable with the timing aspect.

IF all of this were to happen…we’d likely have our first heat wave of the season. The focus of the extended heat would be from next Friday into the early part of the following week at least.

So something to be paying attention too for sure…also of note is the nasty heat building in western Europe up into the United Kingdom. They’re not prepared for anything like this…and there are BIG concerns that a lot of people are in jeopardy from this life-threatening heat. There is not much in the way of A/C there…buildings are meant to keep the heat in and the cold out…it’s a big concern.

The feature photo is from DeAnna Blair in Shawnee