Category Archives: Heat Wave

Extensive period of heat last days to even weeks

Significant heatwave – South West United States – July 2021

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An intense heatwave has gripped the South West United States for much of the start of July 2021 which has seen near record temperatures occur at certain locations and in one case, a possible new temperature record for the United States being the highest “minimum overnight temperature” recorded.

A weather station at Stovepipe Wells in Death Valley appears to have recorded a minimum overnight temperature of 42.1C which was recorded at 5.25 am on July 12 2021. The temperature recordings for this weather station appear to be:-

2 am - 46.1C or 115F.

4 am - 44.9C or 113F.

5.25 am - 42.1C or 108F.

6 am - 43.6C or 110.5F.

If confirmed, this would break the record currently held at nearby Furnace Creek being 41.7C or 107F recorded on July 12 2012.

I travelled to this location in June 2007 and as shown in the attached photo of nearby Badwater Basin just to the south of Furnace Creek, it is easy to see why such high daily temperature extremes occur here year after year.

Minimum overnight temperatures of 40C are rare anywhere in the world but Death Valley is one of a very few places globally where this can occur due to the topography of the region. The mountain ranges to the east and west play a significant role in trapping in the heat of the day allowing little to escape overnight.

In addition, this heatwave has seen a maximum temperature reach 54.4C or 130F at Furnace Creek on July 9 2021 at 5.00 pm. At Furnace Creek, it reached 53.5C on the 10/7/2021 and 53C on the 11/7/2021 which is significant even for this desert location. A temperature of 54.4C could be amongst the highest verified temperature ever recorded anywhere however this is now subject to intense review.

The official recording for this station is attached to the post for July 9 2021 with the 5 pm temperature of 130F (54.4C) highlighted in blue for clarity.

The heatwave has impacted much of the south west United States including inland California, Arizona, Nevada and even into a portion of Utah where the city of St George recorded 46C on the 10 July 2021. What makes this temperature more impressive is that the weather station lies approximately 860 metres above sea level (Almost the same elevation as Orange in New South Wales for comparison).

Lake Havasu City topped 48C or 118F on July 9. Even more remarkable was that at 1.15 am on July 10, it was still 40C (104F) with the overnight minimum dropping to around 36.5C or 97F at 5.15 am and back up to 100F or 37.8C at 7.15 am. This area is also susceptible to intense summer heatwaves due to location and proximity of nearby mountain ranges trapping in the summer heat.

The worst affected cities are Palm Springs, Yuma, Lake Havasu City and Las Vegas. The heat has contributed to fires in California, significant stress to dwindling water supplies and current drought conditions worsening.

Significant hot weather has also occurred across the inland areas of Oregon and Washington States east of the Cascades and across low lying areas of Idaho where several fires burn. There is significant fire activity south east of Crater Lake in Oregon and another significant blaze north of Fresno in California.

The attached satellite photo taken from NASA’s worldview dated Monday 12 July 2021 is showing one of the largest fires so far this season near Klamath Falls in southern Oregon with a thick smoke plume extending hundreds of kilometers towards the north east and impacting the air quality over Boise (Idaho).

The heatwave is starting to ease across the south west as monsoonal moisture increases bringing with it isolated thunderstorms and the potential for local flash flood episodes.

The current heatwave may have set a few temperature records although such records now need to be proven and reviewed prior to the recordings being confirmed within official data.

Intense Heatwave grips Death Valley and SW USA – June 2021

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In 2009 on the Australia Severe Weather website, I did a detailed thread titled “Hot Weather at Furnace Creek Death Valley - California June / July 2009”. During this period, an intense heatwave gripped the locality as well as most of the South West region of the United States. It was also a time where minimum overnight minimum temperatures of 40C were recorded being one of only two places in the world where such temperature extremes can occur.

The discussion thread can be found at:-

This article only relates to the intense heatwave that occurred at that time and describes the topography and why such intense heatwaves often occur here during June to August each year.

Since this article was prepared, there have been other intense heatwaves at this location and surrounding desert regions.

During June 2021, another intense heatwave has gripped this area and on June 17 2021, the weather station at Furnace Creek Death Valley recorded the hottest verified temperature to date for 2021. A maximum temperature of 53.2C or 127.7F was recorded here. This is just shy of the highest ever June temperature of 53.9C.

A temperature of 50.6C also occurred at Palm Springs east of Los Angeles during the same heatwave.

As described in that thread, much of the heat that occurs here relates to the topography and location. The valley sits between the Armogosa Range to the east and the Panamint Mountains to the west where peaks top 3,368 metres at Telescope Peak. The valley at Badwater Basin sits 86 metres below sea level. During the summer months, heat is trapped over long periods and little escapes during the night. The locality is also within an intense rain shadow so that the air that reaches the valley is extremely dry.

The photos attached to the post are taken in June 2007 following a trip into the valley. The photos clearly show why it becomes so hot here and why maximum temperature records are capable of being broken.

Typically, there is no vegetation available, no water and no relief from the incessant heat.

Weather stations have been placed within the valley to record the extremes of weather and 50C days are common during the summer months. The primary station is at Furnace Creek (Greenland Ranch) just to the north of Badwater Basin. On July 10 1913, it is claimed that it reached 56.7C, here (just to the north where I took the photos) which is the highest maximum temperature recorded. Although while it is accepted by the World Meteorological Organisation, it is still in doubt for a number of reasons, one of which it was recorded by an untrained observer and that the observation may be inaccurate.

A look at the National Weather Service forecasts for this region for the next seven days clearly shows that heat advisory warnings and excessive heat alerts are being issued for much of the desert south west of the USA with forecast highs of up to 118F (48C). A look at the forecast for Furnace Creek for Sunday and Monday 27 and 28 June shows that temperatures are expected to reach 123F (51C) and 124F (51C to 52C) at the Furnace Creek Visitor Centre or immediate environs.

Similar alerts are being issued for places such as Palm Springs and anywhere within the eastern deserts of California and western Arizona.

The current heatwave that is occurring is intense even for such locations and such heat will continue throughout July and August which are the typical summer months.

Heatwave Conditions SE Australia – 22-26 January 2021

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A significant heatwave has gripped south east Australia over the past 4 to 5 days and is presently ending due to a cool change that is slowly crossing the southern part of the continent.

This event has been most noteworthy across the inland regions of Victoria and New South Wales although it has been strong enough to spill over into parts of Western Sydney although generally west of Parramatta.

As shown in the plots produced on the “Water and the Land”, for temperature, the worst affected regions haves been the south west part of New South Wales, Northern Victoria and South Australia.

There has also been a major bushfire emergency in the Adelaide Hills although a cooler change and at least 20 mm of rain has helped fire fighters to contain the blaze.

Maximum temperatures within the worst affected regions have included:-


Friday - 37.6C, Saturday - 37.6C, Sunday - 39.8C, Monday - 39.8C.


Thursday - 37C, Friday - 39.2C, Saturday - 40.8C, Sunday - 41.7C, Monday - 40.4C.


Thursday - 38.2C, Friday - 39.9C, Saturday - 40.8C, Sunday - 43.6C, Monday - 41.7C.


Thursday - 37.5C, Friday - 39.6C, Saturday - 41.5C, Sunday - 42.3C,

Other significant temperatures during the event include

Yarrawonga - 40.8C on Saturday.

Ivanhoe - 40.7C on Saturday,

Wilcannia and Yanco - 42C on Monday.

Walpeup (NW Victoria) - 43.9C on Sunday.

Mildura (NW Victoria) - 40.4C on Saturday and 43.3C on Sunday.

Swan Hill (NW Victoria) - 41.8C on Sunday.

The most affected regions are those that have not received the benefit of the recent rainfall.

Sydney has generally missed the worst of the heat although some has spilled into the Sydney basin affecting mainly areas away from the coast being the inland suburbs of Blacktown, Penrith, Camden, Richmond and Campbelltown. Anywhere further east has been cooler due to the sea breezes.

Even with maximum temperatures forecast to reach between 36C and 41C across Sydney, it is coming ahead of a cooler change Tuesday night / Wednesday morning.

Maximum temperatures during this event have included (Penrith east to Sydney as an east to west cross section):

Penrith - Friday - 37.1C, Saturday - 38.1C, Sunday - 39.9C, Monday 39.3C.

Blacktown - Friday - 36C, Saturday - 34.24, Sunday - 39C, Monday 37C.

Parramatta - Friday - 35.8C, Saturday - 33.3C, Sunday - 33.8C.

Sydney (Observatory Hill) - Friday - 32.9C, Saturday - 31.9C, Sunday - 33.9C, Monday 32.1C.

This gives some indication that the level of heat being experienced across the inland suburbs is not progressing east beyond Parramatta. However, it is noted that it has reached 30C at Sydney Observatory Hill on 4 days in a row and if the 36C is reached for the 26/1/2021, this would result in 5 consecutive days where it has reached 30C which is not common in summer.

A feature of this event for the Sydney basin were the development of an isolated thunderstorm on Friday afternoon (Over NE Sydney), Saturday afternoon that produced flooding at Marsden Park (Covered in a separate article) and another isolated storm cell on Sunday afternoon across the Blue Mountains as shown in the attached photo looking west. This storm did not make it into the Sydney basin but the anvil cloud cover and later additional cloud provided some relief Sunday afternoon from the heat although it made for a warm uncomfortable night.

The cool change across the south has brought welcome rain including 16.8 mm at Deniliquin and 12 mm at Mildura and useful totals of up to 29 mm over the Dandenong Ranges (East of Melbourne). The cool change will progress towards Sydney Tuesday and conclude this current weather event late Tuesday / early Wednesday for Sydney and much of New South Wales.

Addendum 26/1/2021 - On Tuesday maximum temperatures reached 37.1C in Sydney City (Observatory Hill) making it 5 days in a row where maximum temperatures have reached 30C. Other maximum temperatures include 41.6C at Sydney Airport, 41C at Sydney Olympic Park, 40.7C at Penrith, 39.8C at Richmond and 39.1C at Horsley Park.

Most areas of Sydney has topped 38C to 41C with minor variations and it is noted that maximum temperatures were reached between 2 pm and 3pm. Increasing cloud cover from the approaching cool change after 3 pm is resulting in a slow drop in maximum temperatures and as such the worst of the heat has now passed.

It also reached 39C at Coonamble and over 36C at Dubbo but the cool change is having a significant effect across New South Wales, lowering temperatures, producing some light rain / showers especially to the south and concluding this weather event.