July 06, 2024

Unbelievable Change in Temperature in a Very Short Distance

Can you imagine having the temperature change from a chilly 59F to a torrid 101F in only 3 miles?    Or a similar change ascending a modest mountain, with temperature INCREASING with height.

All this happened today in the Bay Area.  Perhaps this should not surprise us considering the craziness of San Francisco!

Consider the high temperatures today around the Bay Area.  59 F on the Pacific side of San Francisco, but 101F at the top of Mount Tamalpais, at around 2500F.   Even higher (105F) at a nearby mountain site.  About 40F change from Stimson Beach on the Pacific to the top of Tamalpais.....3 miles away.


Stunning contrasts.

This situation was characterized by the very cold water of the Pacific and an associated shallow cold air layer near the surface with an extraordinary inversion capping the cold air.

Below is an analysis of the sea surface temperature of California. (sorry, it is in centigrade),  Very cold water is found along the coastal zone of California, the result of upwelling cold water from below.

How cold?  About 9C or about 48F.  Wow...very cold.  This cold water chills the air right above.

We can check out the vertical temperature structure in the area using the ballon-launched radiosonde released at Oakland, CA this morning at 5 AM (see below).  Height is in pressure (850 is about 5000 ft, and the temperatures are in °C).  The right line is temperature, and the left line is dewpoint.

Mama Mia.  Was there an inversion!   A shallow, cool, saturated layer was apparent in the lowest few hundred meters, with a huge inversion overhead in which temperature increased from 14C to 35C (57 to 95F) in about 1500 ft.

What about our area?

Some impressive coastal contrasts exist today, but not in the same league.  Our coastal water is not as cold and the contrasts stretched over more distance.   To illustrate, here are the high temperatures today on the central WA coast.  60s on the coast and about 101F in the inland low terrain.  Still impressive.

Acknowledgment:  This amazing situation was brought to my attention by Dr. Peter Benda.


  1. Used to live in the Sacramento Valley, in a house without a/c. The ocean was our air conditioner. When a heat wave was on the way, we'd pile in the car and camp by the ocean.

  2. This is really fascinating information. "Location, location, location" definitely applies to all-things-weather, and it's small wonder that generalizations about conditions vary as wildly as they do. Folks participating in a recent "Watts Up With That" podcast (just a day or two ago, it may be on YouTube at this point) discussed how misleading figures can be, based on instrument location(s) ...that is, that many instruments (particularly "temperature sensors," thermometers) are sited near buildings, pavement, etc.

  3. Best contrast I've seen locally was in 2021 June at KSEA at 104f with 71f at the Des Moines Pier, about 3 miles as the crow flies difference.

  4. Sunday, July 7, 4 PM.

    97˚F in the shade in the NE corner of my front deck*, 24 % RH just west of the Washington Park Arboretum (East Capitol Hill).

    72˚F / 63% RH in my unfinished basement in my un-airconditioned house, .00473 miles away (25 ft. +/- 5 feet and about 4 ft. lower in elevation).

    My house main floor, with windows sealed shut and curtain and blinds pulled shut to control the photons of light entering the house is 83˚F / 52% RH with one floor fan operating to stir the air. This is actually fairly cool for such hot days. Maybe it's my imagination, but ever since I started leaving my windows shut on very hot days, the inside of my house stays a little cooler. It's helped since I've installed double-pane, UV-coated windows a few years ago. This house was originally built in 1909 and had single-pane glass through much of it, most of the old windows unopenable.

    I was assembling some summer furniture out on the deck in that corner about 2-3 PM, but it became too hot. I brought my tools back in and gave that task a rest. I stuck a thermometer out there on the partly assembled furniture just to see how hot it might be.

    I've lived in Seattle for 40 years and this house for nearly 25 of those. I've always thought Seattle summers were right on the edge of justifying air-conditioning but I've never had it here. I made it through the 108˚F June day in 2021 just fine, though I spent much of that afternoon sitting on a folding chair in the cool basement catching up on reading. That day my main floor was 100F. The basement was a cooler 90F. Today, after coming back indoors due to the heat, I went to the basement to straighten it out. And stay cool.

    I've taken a lot of walks in the surrounding neighborhoods the past few years. The walks are about 6-7 miles each and I typically take 2-3 per day. I took my first one this morning before the heat kicked in, through shady Interlaken Park and down along the shore of Eastlake. Still had the hill climb up and over Capitol Hill. That's a burner even in the winter. It's been especially so the past few days. I've got a second walk after dinner when it cools off a bit.

    It's been amazing the number of HVAC and AC installation vans I've seen on these walks parked outside peoples' homes in this city the past few years. It's been very noticeable, especially after the June 2021 heat event.

    I'm still holding off on A/C. It can get very hot up here in the summer, but the heat spells are relatively short and the natural AC usually kicks in soon after. I'm going to try better shading options for my windows first. I grew up in the Midwest (Indianapolis) in the 1960s and 70s. Our brick house in the 60's had no A/C except for the parent's window unit in the late 60's. I remember how brutally hot and humid summer nights could be. From 1971-78, the house we lived in had central air. It made all of the difference. I moved to the west coast in 1978 (SFO/Berkeley/Seattle) and have lived without A/C ever since. Natural AC has worked well in the past out here. I'm counting on it to continue to do so in the future.

    * uncalibrated thermometer

  5. I was noticing the same thing today, though mainly between Neah Bay, where I have spent some time, and parts inland. Looks like it won't hit 70 the entire week there, Thursday topping out at 61, while it'll be in the 90s every day here in the Snoqualmie Valley, 95 today.

  6. I lived in Carmel CA in the mid-80s. I wonder if Cliff's been there in the summer.

    Carmel downtown, 50 degrees.

    Carmel Valley (two miles inland) 105 degrees.

    Around 3pm, if you were on Hwy 1 going toward Carmel, you could see a wall of fog headed straight for the Monterey Peninsula most days. The five summers I spent there were the five most pleasant summer I've spent anywhere.

  7. Cliff, why is it that the sea breeze doesn't go very well when there's a heat wave? I and a friend took the sailboat around Whidbey Island over the weekend. We had to motor most of the way because there was almost no wind Saturday and Sunday. Even Everett, which has fairly reliable NW winds on summer afternoons, was quiet. We baked in the heat the last two days and actually swam in the chilly sound. Got a real treat though, when a group of 4 orcas swam right by our boat while we were anchored. Somehow, a whale watching tour knew where they were and showed up within minutes.

  8. I can't help but question statements being made about changes in the planet's temperature since "pre-industrial" times (what's being reported as figures per the org named Copernicus). The "Little Ice Age" ended in 1850, for goodness' sakes. It's difficult to know how accurate "pre-industrial" data was; I don't know where the data points were, how "long for," and how thermometers were calibrated. When I see and hear figures like "increase of 2.7 C" I can't help but wonder why that should be a shock given that natural planetary mechanics have always been in play, swinging much more wildly through geologic time. Change on this scale simply doesn't seem like big "news."


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

Thunderstorms Return to the Northwest

 Thunderstorms have been relatively rare this summer, but today will see some boomers over the Cascades and eastern Washington. In fact, the...