Cumulus maintains a number of 'all time records' for the station -- highs and lows and their timestamps for many of the readings. For more information on this file see in the Cumulus help file, in the section “The Data log files”.
Pre Build 924 (version 1.8.9)
The highs and lows were stored in a database file (alltime.rec)
Build 924 (version 1.8.9)
Starting with Build 924 (version 1.8.9) of Cumulus highs and lows and their timestamps are stored in a text file which can be easily edited if needed. The first time you run Build 924, or later, of Cumulus it will convert any alltime.rec file into an alltime.ini file and use the ini file going forward.
Post Build 924 (version 1.8.9)
The alltime.ini file is normally located in the Data sub-folder of the path where your Cumulus.exe is installed. If you cannot find the file see this FAQ. Date, Time and Decimal formatting is as per your regional settings on the PC running Cumulus. The format consists of a number of sections (section title is delimited by [ ]), and a number of properties (consisting of attribute name, an equals sign and a value). Blank lines can be included for readability, they are ignored in these .ini type log files.
If you restart Cumulus during the day it will read this file at startup, so it can resume tracking extremes of the key parameters starting from latest stored values in alltime.ini. Equally, if you close Cumulus during the day it will write the final values for highs and lows and their timestamps to alltime.ini as part of the close down process.
Viewing the all-time highs and lows
Editing alltime.ini within Cumulus
Expanding what it says in FAQ: FAQ#How_do_I_correct_my_all-time_.28or_monthly.29_records.3F, the stored values can be corrected using the All time records screen on the Edit menu and this Cumulus editor allows you to read from the daily log or the Monthly_log_files. Therefore, normally any rogue values are corrected in these source files, and resulting lows and highs copied across to the all time log using the in-built editor. However, you can also just edit any low, high or timestamp manually looking at Alltimelog.txt for current and previous values.
Editing alltime.ini outside Cumulus
It is unlikely that you need to do this, given the functionality of the in-built editor.
Tips -- take a copy of the original log file before you work on it outside Cumulus.
Edit the original file using an editor that treats all fields as text [either any text editor, or a spreadsheet program that can be instructed not to recognise special field (like date) types]. All values have to be specified in the correct section, see #Post_Build_924_(version_1.8.9) above and follow the format of the property lines in the example below. Note that figures are held internally in Cumulus in binary, and converted to Base 10 numbers for the value shown. Since fractional binary values cannot be converted exactly to base 10 decimals, real numbers appear to be given to a strange decimal resolution with multiple decimal places. Also note that the timestamp includes a calendar date, so for a 9 or 10am rollover, if you need to manually look for highs and lows for times between midnight and rollover, these would be derived from the daily log (dayfile.txt) row for the meteorological date (the date before the calendar date for those early hours).
Example line of the file
[Temperature] hightempvalue=30.7999992370605 hightemptime=27/06/2011 12:58:00 lowtempvalue=-12.5 lowtemptime=20/12/2010 07:17:00 lowchillvalue=-12.5 lowchilltime=20/12/2010 07:17:00 highmintempvalue=17.2999992370605 highmintemptime=10/07/2010 lowmaxtempvalue=-4.30000019073486 lowmaxtemptime=20/12/2010 highapptempvalue=33.7999992370605 highapptemptime=27/06/2011 12:50:00 lowapptempvalue=-15.8000001907349 lowapptemptime=20/12/2010 07:17:00 highheatindexvalue=34.2000007629395 highheatindextime=27/06/2011 13:09:00 highdewpointvalue=21.8999996185303 highdewpointtime=27/06/2011 13:09:00 lowdewpointvalue=-13.5 lowdewpointtime=20/12/2010 07:20:00 hightemprangevalue=20.3999996185303 hightemprangetime=20/04/2011 lowtemprangevalue=1.29999995231628 lowtemprangetime=31/12/2010 [Wind] highwindvalue=30.7578811645508 highwindtime=12/09/2011 09:08:32 highgustvalue=38.4000015258789 highgusttime=07/02/2011 10:34:00 highdailywindrunvalue=221.78596496582 highdailywindruntime=10/09/2011 23:59:00 [Rain] highrainratevalue=114.300003051758 highrainratetime=23/09/2010 14:13:00 highdailyrainvalue=34.9000015258789 highdailyraintime=17/07/2011 22:19:00 highhourlyrainvalue=15.8000001907349 highhourlyraintime=23/09/2010 22:08:00 highmonthlyrainvalue=103.599998474121 highmonthlyraintime=01/02/2011 longestdryperiodvalue=17 longestdryperiodtime=24/04/2010 longestwetperiodvalue=16 longestwetperiodtime=16/02/2011 [Pressure] highpressurevalue=1043.30004882813 highpressuretime=26/01/2010 10:44:00 lowpressurevalue=965.700012207031 lowpressuretime=08/11/2010 15:42:00 [Humidity] highhumidityvalue=100 highhumiditytime=23/01/2010 01:10:00 lowhumidityvalue=21 lowhumiditytime=24/04/2010 12:10:00