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Cumulus Help

One of the attractions of the original Cumulus software is that the installer installs a detailed set of help screens, so that each screen has a button that you can click for assistance, and the Main Screen has a Help menu where you can look up more guidance, such as web tags. The final 1.9.4 helpfile can also be downloaded (for viewing using Windows Help) from link in resources section below. At the time of typing, it can also be viewed at Cumulus Top Weather Sites. See resources section below for a translation into French.

Upgrade Advice

If you are one of the Cumulus users who has retained the Cumulus version they originally downloaded and not upgraded to final version 1.9.4 build 1099, please read on.

Upgrading your Cumulus 1 version to the final version simply involves downloading the installer package (only the final one is available below)

  • As you run the installer, untick the selection on Components screen.JPG if you want to keep your existing Cumulus Web Templates
  • Upgrading by default installs over your existing files, but does not affect your "data" subfolder so all existing extremes and logs are retained
  • Upgrading does not affect any strings.ini file, although the options for content may be extended by an upgrade (see Samplestring.ini)
  • Upgrading does not affect your existing cumulus.ini file, although there may be additional Configuration Menu options
  • Upgrading will fix most of the bugs in your current version, and offer new functionality, see the changes.txt file that the installer provides.
  • Upgrading to version 1099 allows you to install the 1099.1 or 1099.2 patches, the latest of those allows selection of years up to 2030 in several year selectors that otherwise end at 2020.

Final Cumulus 1 version

Cumulus 1 has now been described as Legacy Software, simply because it is no longer supported, and can no longer be updated (Steve Loft did not share the source code, so it cannot be edited, and the Microsoft environment used for producing Cumulus 1 is no longer available).

If you want to run Cumulus 1.9.4, there is no reason why you should not. It is a stable release, and only one bug has been identified. The single known bug, never fixed even in 1099, is that the original Cumulus software uses the wrong memory location for pressure for Fine Offset models. These weather stations are also considered legacy ones. There is a workaround described within FAQ page.

Date Selection

  • The first public (1.0) release of Cumulus was on 27th January 2004 (Steve Loft had been developing Cumulus just for his own use during much of 2003).
  • As Cumulus developed, various screens were added (history available at Cumulus Versions) involving selections of a date (view month, view year, view period, and view NOAA report)
  • On these you could type any date you like into selection boxes initially, but drop down selections were added allowing you to pick some dates from the drop down boxes that can select some years, and (where relevant) any month and any day within any month.
  • Obviously the day selector has 31 choices (1 to 31) and the month selector has 12 choices (January to December). The year selector also offered a choice of just 12, but the earliest and latest year were advanced in subsequent major releases as the years moved on.
  • Release 1.9.0 was made available on 11 September 2010, and from then (until final 1.9.4 version in 2014), the years available were 2008 to 2020 (In 2014 when Steve Loft last worked on this software the year 2020 still seemed a long way into future).
  • Until the final 1.9.4 build, the software still allowed you to type in years that were not in the drop down, it even permitted selection of non existent dates like 29 February 2009, but the final build removed the ability to select by typing (because Steve Loft was abandoning Cumulus 1 and assumed users would not still be using it in 2020).
  • A Mark Crossley patch can be applied to the final Steve Loft build 1099 software, the patch is basically the code (not the installer) of the 1099 build's cumulus.exe with an edit to one resource module that contains the strings for the dialogs The change made modifies the year drop-down selection to offer now the years 2018 to 2030, making it easier to select years in the current decade (at time of typing this) in the relevant screen box. The other files installed by the standard 1099 installer download are still needed for the patched file to work.

Download Instructions

Please refer to Setup page first, so you understand how the installation process works. A more detailed (but now out of date) guide can be downloaded from Cumulus basic installation guide.pdf.

This is a multi-stage process:

  1. First Download the Windows Installer Package, the CumulusSetup.exe file here.
  2. Choose a location where you will install the software on your Microsoft Windows device (the installer defaults to previous location if one is recorded in the registry)
    • Don't install to "Program Files", any files there can only be updated by an installer, you want your data files to be change while Cumulus is running as data is received!
    • It is best to install to a root of whatever drive has plenty of spare space, this might be where you are using for your working files or normal documents
  3. Now run the installer, so it creates a large number of files and folders,
    Cumulus folder structure.PNG
    • (make sure the files and folders are installed in right location)
    • As you run the installer, read the instructions it displays (see below) Install screen.JPG.
    • This read me text can also be downloaded from a link in the resources section below
  4. When the 1099 installer has completed, there is another download to do.
  5. Now download the 1099.2 patch available here.
  6. Take the file "Cumulus.exe" from the patch, and use it to replace the file "Cumulus.exe" from whichever of the three installer packages you used earlier
  7. All other files from the full 1099 release, must be retained after applying the patch. The patch does not change any of the compiled code, nor its functionality.
  8. Start running Cumulus as instructed on Setup page.

Special Cumulus 1 versions

If you are an Instromet user, and your logger operates at 115200 baud, you should use special build 1100 at special 1.9.4 build 1100.

If you are an Instromet user, and your logger operates at 19200 baud, you should use special build 1101 at special 1.9.4 build 1101.

The patch, mentioned in download above, can NOT be applied after installing either of these special versions, it changes the GUI to make the drop down list cover years 2020 to 2030, but it is basically the 1099 build code so that does not include the Instromet specific code.

Additional guidance

If you need any help with Cumulus 1, see if your question is answered, in this Wiki, on the original Cumulus software's FAQ page. If you cannot find your answer on that page, then use the correct C1 support forum to see if others have answers.


  • Cumulus installation guide Instructions for installing Cumulus 1
    • (this 1 June 2010 edition is now out of date,
      1. as it gives out of date Universal Resource locators, quoting Steve Loft's hostname for Wiki and support forum
      2. as it relates to Microsoft Windows Operating Systems that are no longer available)
  • Cumulus readme.txt Please read this before installing or updating Cumulus
  • The "Microsoft Windows Help format" text files:
  • Cumulus Realtime An obsolete Silverlight application for displaying real time Cumulus data on a web site (no longer developed or supported)

Earlier Versions

Steve Loft, as well as updating the support forum with announcements about his releases for Cumulus 1, maintained an abbreviated summary in changes.txt, find it at It covers releases back to version 1.0, the first release on 27 January 2004, although the documentation for a small range within that was lost.

For the way dayfile.txt changed between versions, see that link.

For the logs created each month, see the example lines below:

0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	
Date (dd/mm/yy)	Time	Temperature	Humidity	Dew point	Wind speed	Recent high gust	Average wind bearing	Rainfall rate	Rainfall so far	Sea level pressure	Rainfall counter	Inside temperature	Inside humidity	Current gust	Wind chill	Heat Index	UV Index	Solar Radiation	Evapotranspiration	Annual Evapotranspiration	Apparent temperature	Max Solar radiation	Hours of sunshine	Wind bearing	RG-11 rain today	rain since midnight	
30-09-10	21:00	15.3	94	14.3	20.2	35.6	358	10.8	46.8	991	73.5	25.8	60	28.1	14	15.3	0	0	(version 1.9.0)								
22/04/11	10:30	8.1	96	7.5	13	20	142	0	0	1013.28	215.2	20.2	53	11	4.8	8.1	0	216	0.08	171.88	3.3	673	0	(version 1.9.1)			
01/10/11	04:40	18	75	13.5	5	6.7	169	0	0	1021.4	885.3	24.4	61	5.6	18	18	0	0	0	0	17.5	0	0	158	(version 1.9.2)		
01/05/12	04:40	18	75	13.5	5	6.7	169	0	0	1021.4	885.3	24.4	61	5.6	18	18	0	0	0	0	17.5	0	0	158	0	(version 1.9.3)	
02/10/13	22:40	14.2	99	14.1	0	0.7	207	0	0.3	29.85	961.5	119.5	53	0.7	14.2	14.2	0	0	0	0	15.5	0	0	225	0	2.4	(version 1.9.4)

Note about this article

It appears there was a bit of conflict between Downloads page and Software page. The main page previously said "We've added download links for Cumulus V1 and Cumulus MX in the new Software/Downloads page " because of this. Since then the original Main Page has been updated, the legacy Cumulus and Cumulus MX links are now in separate columns of the table, and the introductory text has been revised.

  1. When Steve Loft was about to retire from involvement with Cumulus, he wanted to close his web server.
    • His server ( had hosted the wiki, the support forum, and some of the downloads were at
    • The other downloads (used mostly for beta and special releases) were at which was also closed.
    • In October 2018, Ken True ("saratogaWX") offered to host the Wiki on his site.
    • The Cumulus 1 software files were downloaded from the links just mentioned, and then added to this "Downloads" page by Ken as part of the migration of the Wiki.
    • Ken True added links to the help file download and the Cumulus 1 special downloads for Instromet.
  2. On 31 October 2018, Ken True, downloaded the final Cumulus MX release made by Steve Loft (from his Support Forum post) and created a new Page called Software for this.
    • Subsequently he added the source zip that Steve Loft made available (the source included some changes not in that Steve Loft
  3. The next month (November 2018), Steve Loft sought a new host for the support forum, as next part of closing his web server.
    • When Niall Malpeli-Hosiene ("Freddie") took over hosting of the forum, Ken True updated the relevant Wiki pages here.
  4. On 7 December 2018, Mark Crossley decided to take on further development of Cumulus MX
    • Mark added copies of Steve Loft's MX-beta release, and the released MX source to Marks' Github repository he created for Cumulus MX.
    • As Mark has developed MX further, he has added to this Github repository, the release complied code, the supporting files, and therefore the source files
    • Mark maintains the links to the Github repository for the latest release on the Software page of this Wiki.
    • The early releases by Mark continued to be labelled "beta release", but soon Mark brought MX out of beta, so links were described as "current release"
  5. In March 2019, Niall Malpeli-Hosiene (Freddie) edited the new Software page to make it one destination for both the "primary product" (MX) and what he renamed "legacy software" (original Cumulus 1), in removing the original "Downloads" page, he overlooked that other pages in this Wiki were still linking to the original Downloads page.
    • He was so keen to promote MX, his downgrade of Cumulus 1 to legacy, created some confusion by hiding some links that were still applicable in a MX world below Cumulus 1.
    • Mark made some changes to Neil's design for the Software page in October 2019, but there was a subsequent rollback to the "Freddie" March 2019 design

In April 2020:

  1. this wiki page was resurrected so the links to it from elsewhere in this Wiki worked again
    • this resurrection has given the chance to make this page devoted to Cumulus 1, and so much simpler and more detailed again
  2. the Software page has been improved by Ken True, grouping some downloads in a resources section
    • David (Water01) made some further changes to the Software page re Weatherlink converter and Weather Display
    • the Software page legacy section is currently a prećis of the detail available on this page, as it does have links to Cumulus 1 and the patch.