Hottest AVERAGE Day of the Year.

I posted this question before, possibly even on these boards. But that is irrelevant. Because I apparently posted it the wrong way.

I asked what was the hottest day of the year. And some wiseacre replied it is the day of the year with the hottest temperature.

So you see why I doubt I posted it here. SDMB members usually are more polite (if that is the right word).

Put a better way, what is the hottest AVERAGE day of the year? And why is it so? When does the summer season really begin?

Astronomically, the summer begins on the summer solstice. But where I live (Detroit), weathermen claim it begins on June 1st. I actually have been watching the weather forecast for a little while now. And they usually give the average for the day.

FWIW, the temperature averages are steadily going down now. That process seemed to begin around July 20th, which has me even more confused. If the meteorological summer begins June 1st, the dead center of the season would be July 15th or thereabouts, wouldn’t it?

Thank you in advance for all your helpful replies:).


This doesn’t give the average temperature for each day, but highs and lows, but it appears from this that July 12-29 are tied for Detroit with an average high of 85 degrees.

Well, the hottest day of the year where? In Chicago, the hottest average temperature gets up to 85 and, starting as early as July 16, it slowly begins to decrease.

First, summer doesn’t begin on the hottest day of the year, although that day may roughly signal the midpoint of summer.

Second, where? In Australia (astronomical) summer starts December 21.

Third, weather does not give a shit about the calendar. If you tried to set season start and end dates based on weather it would be shifting every year.

*Astronomical summer *begins on the solstice. Meteorological summer begins June 1 (in the northern hemisphere). The definitions are different because the two groups are interested in different things.

Just to point out how many ways of specifying summer there are:

From Wikipedia: “In Sweden and Finland, meteorologists use a non-calendar based definition for the seasons based on the temperature. Spring begins when the daily averaged temperature permanently rises above 0 °C, summer begins when the temperature permanently rises above +10 °C, …”

In Iceland it’s the first Thursday after 18 April.

In the Irish Calendar, summer begins on 1 May and ends on 1 August.

Note that the summer solstice is traditionally Mid-summer. So hardly the start of summer. Etc.

Even in the US a lot of businesses, etc. consider summer to run from Memorial Day weekend to Labor Day weekend.

here in my corner of the Mojave desert summer weather can start in march and go to November

and the average temperature is 100-112 funny thing my house thermometer it always 4 degrees hotter or colder than what the official temp is

“Summer” is when it gets hot. “Winter” is when it gets cold. “Spring” is when it’s transitioning from cold to hot. All of these are vaguely defined, with fuzzy lines between them, but it can be convenient to set arbitrary boundaries. The astronomical fourcorner days are one simple choice of arbitrary boundaries. The transitions between months are another simple choice. Public holidays like Memorial Day and Labor Day are another. You could, I suppose, look at historical records for a location and take three-month running averages of temperature, modulo a year, and then define the three-month period when that average is hottest as “summer”, but that would be a lot of work, it’d be different for every location, it’d shift over time with climate change, and it’d be approximately the same as the simple methods, anyway.

June 21st is (about) the longest day of the year … but not the hottest … we have what’s called “thermal lag” on land … even though the daytime on June 31st isn’t quite as long as June 21st, the ground is still warming up …

I’m looking at Des Moines, Iowa as the arch-typical example of just about anything weather … it takes until July 11th through July 16th until the ground has warmed up to it’s maximum temperature, and this is when we find our hottest average air temperatures at this location …

Thereafter as the daytime becomes shorter the land starts to cool down … thus the maximum temperature “lags” behind the longest day a few weeks …

Same for the daily maximum temperature, not at local noon but a few hours after … typically 3pm … and then another peak at around 5pm Monday through Friday, although this secondary peak is of “unnatural” causes (i.e. rush hour traffic) …

This page has a map showing the average day for the largest high temperature of the year based on temps from 1981-2010 (clearly, this shifts depending on the years used for the average, so YMMV). There’s also an explanation for why this doesn’t strictly coincide with the longest day of the year (in short, the further you are from large bodies of water, the closer to Midsummer the temperature will tend to peak - the correlation isn’t perfect of course). Deep in the desert, this may occur in late June but you can see from the map that peak summer temperatures occur, on average, in mid to late August for parts of the California coast and large swaths of Louisiana, Texas, Mississippi, and Arkansas.

But as an aside, the Space City Weather site is a great resource for the Houston area. They occasionally also have more general weather information, particularly on tropical storms/hurricanes and the types of weather issues we typically see along the coast. They will occasionally touch on unusual weather in other parts of the country to satisfy site visitors’ general curiosity.

Around here the highest daytime temperature of the year will typically hit between July 5-28. But the warmest nights are a little different, July 11-19. And if you put the highest highs and the highest lows together, they typically fall July 11-18.

The all-time highest temperature was on July 14, 1954, so it fits in this case. But I’m pretty sure it isn’t a given.

The hottest days where I live are in mid-April, not by coincidence the time of the Songkran Water Festival. Our coldest days are near the December solstice when the Sun is lowest in the sky, but Summer is a different matter. Unlike temperate North America where the sun is highest at the June solstice, our sun is highest (at zenith) in late April and then again in mid-August.

I’m not really sure why our Aprils are hotter than our Augusts; I suppose it’s related to the rainfall cycle.

I assume this means you live within 23.5 degrees of the equator. Then the sun wold actually be north (south if you live in the Southern Hemisphere) of you at noon on June 21. It would be straight overhead at noon on two days equally spaced around that.

Yeah, that’s what I said. … Except that the Sun is to the north on June 21 even if you live in Southern Hemisphere. :slight_smile:

The summer solstice here in Aus is Dec 21, but the weather gets HOTTER at the end of January and into Feb…often extending into March.

Go whinge to those who did the Solstice Calendars. :smiley:

The summer solstice is commonly known as midsummer, which is hard to reconcile with the fact that some people count it as the start of summer.

As others have pointed out, the seasons are fairly flexible. Much of the globe doesn’t have four distinct seasons and, in those parts that do, the seasons are quite variable, depending on climate, geography and culture.

In central Thailand we speak of three seasons: dry-hot, rainy-hot and cool. I know a guy from southern Thailand who describes three seasons all named “wet” — wet from rain, wet from flood, wet from perspiration.

In recent years the weather has been deviating from its old patterns. My sister-in-law has a punchline for that: “Thailand is becoming a developed country now; we have FOUR seasons!” :slight_smile:

In Panama, we have two seasons: the dry season from mid December to late April, which is called the summer (verano), and the wet season or winter (invierno) from late April to mid December. Both seasons are hot, although the wet season is a degree or two cooler on average (but the dry season is more pleasant because it is windier and less humid). “Summer” activities, such as school holidays, the baseball season, and going to the beach take place during the verano.