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.

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.

Tuesday

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.

Wednesday

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.

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.