Does the mercury spike at the end of the day?
July 23, 2012 4:20 PM
Does the mercury spike at the end of the day?
I have a theory, based on a year or two of casual observation, that on a summer day the temperature tends to spike a bit near the end of the day, say 5-6pm. Is this a thing?
My observation has been that if it is say 20c around 3:00pm and I head out after work, say 6:00pm, and check the temp again it seems to very often be a few degrees hotter just before it starts to cool down.
I have a theory, based on a year or two of casual observation, that on a summer day the temperature tends to spike a bit near the end of the day, say 5-6pm. Is this a thing?
My observation has been that if it is say 20c around 3:00pm and I head out after work, say 6:00pm, and check the temp again it seems to very often be a few degrees hotter just before it starts to cool down.
Go to www.accuweather.com, click forecast, then hourly. You'll see the hourly temperatures. The lowest is usually about 5 or 6 AM, the highest between 3 and 4 PM.
posted by StickyCarpet at 4:28 PM on July 23, 2012
posted by StickyCarpet at 4:28 PM on July 23, 2012
That is consistent with my experience measuring the temperature of indoor (not air conditioned) space. During the summer, the daily peak was almost always right around 6pm. (Massachusetts, fwiw)
posted by sriracha at 4:30 PM on July 23, 2012
posted by sriracha at 4:30 PM on July 23, 2012
You are not wrong! Here's an explanation.
In Seattle, we sometimes hit the daily high after sunset during the summer. It's very counterintuitive but there you go.
posted by adiabat at 4:32 PM on July 23, 2012
In Seattle, we sometimes hit the daily high after sunset during the summer. It's very counterintuitive but there you go.
posted by adiabat at 4:32 PM on July 23, 2012
Check out WeatherSpark for a nice graph of temperature vs. time, for any location you like.
posted by BrashTech at 6:09 PM on July 23, 2012
posted by BrashTech at 6:09 PM on July 23, 2012
There's a similar effect where the annual temp is warmest somewhat after midsummer. It may depend on how far from the equator you are. In Britain August often seems the warmest month because it takes a while to heat up.
posted by anadem at 6:16 PM on July 23, 2012
posted by anadem at 6:16 PM on July 23, 2012
Indoor space will always lag the outdoor temperature because the building has more thermal mass than the outside air.
posted by gjc at 6:21 PM on July 23, 2012
posted by gjc at 6:21 PM on July 23, 2012
I heard a few people (elementary school kids) talking about this a couple of decades ago.
Assumption #1: The sun at its highest peak and thus greatest exposure = highest heat.
Observation: The instantaneous amount of photonic energy is highest, yes.
Analysis: It takes time for energy transfer. Like that big file you tried to download - a 30 minute video file might take 3 or 4 hours to download, depending on you connection.
The sun warms surfaces quickly, the air less so. There's also loads of local microclimate stuff to take into account, but the basic idea is that air takes a long time to heat up whereas heat from direct radiative heating (photons hitting you) is a lot faster. So, at noon, you get lots of sun and get warmed from radiative heating, by the afternoon, the sun's also heated up a lot of the air, and even though it isn't heating you by throwing photons at you, the air's warmer and it's stiffling and there is a much lesser temperature gradient between your skin and the air which makes it feel hotter to you.
posted by porpoise at 8:56 PM on July 23, 2012
Assumption #1: The sun at its highest peak and thus greatest exposure = highest heat.
Observation: The instantaneous amount of photonic energy is highest, yes.
Analysis: It takes time for energy transfer. Like that big file you tried to download - a 30 minute video file might take 3 or 4 hours to download, depending on you connection.
The sun warms surfaces quickly, the air less so. There's also loads of local microclimate stuff to take into account, but the basic idea is that air takes a long time to heat up whereas heat from direct radiative heating (photons hitting you) is a lot faster. So, at noon, you get lots of sun and get warmed from radiative heating, by the afternoon, the sun's also heated up a lot of the air, and even though it isn't heating you by throwing photons at you, the air's warmer and it's stiffling and there is a much lesser temperature gradient between your skin and the air which makes it feel hotter to you.
posted by porpoise at 8:56 PM on July 23, 2012
Check out WeatherSpark for a nice graph of temperature vs. time, for any location you like.
posted by BrashTech
That's better than accuweather, and today it does confirm the times I gave. I find the daily graph of temperature, and the different but mostly the same shapes it transcribes to be very interesting.
When an odd shape occurs I can note it, maybe call it a lucky shape, when the usual shapes occur I am reassured.
posted by StickyCarpet at 6:14 PM on July 24, 2012
posted by BrashTech
That's better than accuweather, and today it does confirm the times I gave. I find the daily graph of temperature, and the different but mostly the same shapes it transcribes to be very interesting.
When an odd shape occurs I can note it, maybe call it a lucky shape, when the usual shapes occur I am reassured.
posted by StickyCarpet at 6:14 PM on July 24, 2012
but... the answer you marked (adiabat's) links to an article (and chart) which, though it does talk about lag, disproves your conjecture, showing the daily high temp at 3pm, not 5 or 6pm.
posted by at at 4:38 AM on July 26, 2012
posted by at at 4:38 AM on July 26, 2012
daily high temp at 3pm, not 5 or 6pm.
posted by at at 7:38 AM
Yes that's normal for ambient temps, but that raking evening sun does sometimes effect my outdoor temp sensor, giving high readings.
posted by StickyCarpet at 9:28 PM on July 26, 2012
posted by at at 7:38 AM
Yes that's normal for ambient temps, but that raking evening sun does sometimes effect my outdoor temp sensor, giving high readings.
posted by StickyCarpet at 9:28 PM on July 26, 2012
This thread is closed to new comments.
posted by weapons-grade pandemonium at 4:24 PM on July 23, 2012