Summer is here: Let’s talk heat forecasting

In brief: Today’s post talks about the arrival of summer-like weather in Houston, and breaks down the four phases of summer. We also discuss a new offering from the National Weather Service called “HeatRisk.” Finally, we look ahead to a hot and sunny Memorial Day Weekend.

We’re starting to see 90-degree days on the regular which, in my mind, signals the start of summer in Houston. Long-time readers will know that I like to break summer down into four phases. Why? Because “summer” season lasts so long, nearly five months. This is contrast to meteorological summer, which runs from June through August, and “solstice” summer, which runs from June 20 through September 22 this year. For me, Houston’s summer typically runs from about mid-May through mid-October. Here are the four phases:

  • Early summer: When we first start to see 90-degree temperatures with regularity, but some nights in the 60s are still possible, and there’s still the thinnest hope of a weak front
  • Mid summer: When highs run from 90 to 95 degrees, and nights are sultry, but you know it could still get worse
  • High summer: Somewhere between late July and early September there’s a period where temperatures reach the upper 90s to mid-100s and you realize, “Ok, this really is the worst.”
  • Late summer: This is the period in September and early October when days grow shorter and we usually see the first front or two of the season. But most of the time it’s still hot.

Early summer began this week in Houston, and we have a chance to bump into Mid summer early next week before we drop back into early summer. You may think it’s crazy to have gradations of heat during summer, as Houston is invariably hot and humid during the summer months. But as we found out last year, there is heat and there is heat. Last summer we used the “wet bulb globe temperature”to measure how hot it really felt outside, and we’ll continue to use this tool. However there’s now another way to assess the heat.

HeatRisk map for Monday, Memorial Day. (National Weather Service)

This year the National Weather Service is introducing a “HeatRisk” color-based scale that takes into account the following factors to provide guidance for outdoor activities:

  • How unusual the heat is for the time of the year
  • The duration of the heat, including both daytime and nighttime temperatures
  • If those temperatures pose an elevated risk of heat-related impacts

The scale ranges from green (little or no risk) to magenta (extreme). If we look at the risk for Memorial Day we can already see a few areas of Houston reaching an ‘extreme’ level of risk. This is due to temperatures likely in the mid- to upper-90s and the time of year, late May, as we’ve not re-accustomed ourselves to the heat yet.

In any case, feel free to use this planning tool as we go through the summer.


We’ll see a few more clouds today than we saw on Monday, and this should help hold temperatures to about 90 degrees. Winds will be from the south, at 10 mph or so, with gusts up to 20 mph. Aside from that it’s going to be another humid day, with a warm night in the mid- to upper-70s.


Skies should be partly to mostly cloudy on Wednesday, and this should allow some parts of Houston to stay in the upper 80s. However, if we get a bit of sunshine during the afternoon hours, highs in the low 90s are possible. Still warm. Still humid.

Thursday and Friday

These days will probably bring mostly sunny skies, so temperatures from 90 to the low 90s are likely. Nights remain warm.

Wet Bulb Globe Temperatures will be high this week, but not extreme. (Weather Bell)

Saturday, Sunday, and Monday

Hot and mostly sunny. Highs this weekend are likely to reach the mid-90s, with upper-90s possible on Memorial Day. By Monday it looks like a weak front will approach the area, bringing a chance of rain with it. However I don’t believe this front will arrive in time to modify conditions during the daytime on Monday.

Next week

The front should arrive on Monday night or Tuesday, and at this point it does appear as though the boundary will indeed push all the way to the coast. Don’t expect miracles in late May, but we might see some slightly drier air and highs in the upper 80s, with modestly cooler nights. It isn’t much, but it’s the best we can reasonably hope for at least the next three months, and probably longer.

42 thoughts on “Summer is here: Let’s talk heat forecasting”

  1. Not shooting the messenger but stating the obvious: there’s something wrong about a 5-month summer.

  2. The NWS shows the WBGT values for each category of heat stress. It might be helpful to also include those temperatures ranges. I use a Kestrel 5500 to get accurate WBGTs and then look at the chart for heat stress levels at my house.

  3. As much as I appreciate space city, I am a bit frustrated that you were unable to predict the storm. Esp 6 days later and we don’t have power.

    • It was a high level weather alert day.
      How would their prediction have helped your power situation?
      At the end of the day, we humans need to understand that we cannot predict or control everything. Stay humble.

    • I agree it was a swing and miss on the forecast. But if the storm had been accurately forecast would it have made any difference?

    • I know its frustrating not to have power after 6 days, but this is 1000% not SCW’s fault your power went out, and if they had been able to predict this it still wouldn’t change the fact that you lost power. My husband is on storm restoration for CNP and I can assure they are working hard 16 hours a day to get your power back on. Not having power in the heat is awful so I do feel for you.

      • Stop pretending like Htown isn’t a disgusting swamp, can’t blame anyone for wanting to leave.

    • I hope to find myself about 650 miles to the northeast in a couple of years myself. Ten degrees cooler year round, no hurricanes. Snow now and then!

      • Would that be Kentucky or Tennessee? It is a lovely part of the country but I’m not sure of the efficacy of actually living there. It’s nice a woody but I have seen and read ‘Deliverance’, so I wonder how long a piece of ripe fruit from Texas would last.

        • My parents retired to Crossville, TN – it’s a little too dull for me. I’m thinking somewhere between Nashville and Huntsville along the I-65 corridor. Knoxville and Greenville are also on the list – I have several friends in Knoxville. It’s also close to where my great-great grandfather and grandmother on dad’s side were born – yes, I’m descendant from Tennessee mountain men.

          • North Carolina in the Asheville area would be nice, very popular so very expensive, too pricey for me, sadly.
            I could probably sell my house and afford to buy a cabin with an outhouse and sans running water, I suppose, is that the sort of nostalgic thing you are after – mountain man?

  4. I’m a fan of the 2-phase “summer” and “super summer” classification. (Maybe just me but seems a bit odd to jump from early to mid to early summer within the same (early summer) week?)

  5. June is supposed to be the wettest month of the year in houston. Why are we assuming it is the end of the spring storm season; and why did it end up so dry the past two years?

  6. We had a pretty good run of days under 90 degrees…

    Now let’s hope for a summer without any 100 degree days or as few as possible. In both 2021 and 2014 we did not hit a 100 degrees.

  7. Definitely going to get a generator after this huge wake-up call, always hoping we don’t need it, but it’s worth being prepared (and having cold drinks and wifi).

    • We put one in after the freeze. It’s nice to not worry. And to be able to help the neighbors if needed.

  8. I’m getting nervous about no rain in the forecast – really hoping we do not have another drought like we’ve had in the last two summers. It’s been hell for people’s foundations, driveways, sidewalks, roads and yards.

  9. This is nice but I really wish we could focus on rain patterns instead of heat. The heat can get annoying but people have ACs and nobody really spends time outside in this city. It’s the rain that’s important as can create havoc and at the same time, lack of it can cause drought. It’s obvious you guys don’t like the heat but it’s the south so… just get used to it. To me it’s more important to know how much rain is falling, where it can flood the most according to rivers/bayous, storm tendencies, winds, tornado paths in the city, etc. Of course I am just one reader. It seems like all the other ones just love to throw hate at summer. It’s my personal favorite time of the year. I like seeing green and I love getting the pool.

    • Working in my garage or in my yard, I would definitely like to hear about the heat.

      This especially applies to my coworkers who are mostly field-based jobs and need to know what their water intake needs to be.

    • Heat kills. A lot of people in Houston don’t have reliable A/C sadly. Elderly especially. It’s important to report on both.

  10. The problem is in recent years we go from a brief period of early summer straight into late summer in June. I remember when we used to have somewhat of a transition period from normal hot summer weather in June and then the true scorching heat would start in July. There were a few exceptions throughout history. But now we head straight into August like weather in mid June now. And the dew points have been off the charts in recent years. That will only get worse.

    • Yup. At least 20 years ago you could take a walk around dawn without returning drenched in sweat after walking through a steam bath.


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