# Extremely high value of ERA5 monthly total precipitation **URL:** \ **Category:** C3S - Datasets and Usage\ **Tags:** era5\ **Created:** [26 May 2026 08:16 UTC](https://forum.ecmwf.int/t/extremely-high-value-of-era5-monthly-total-precipitation/15010 "2026-05-26T08:16:36Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Wenqi\_Cheong](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/w/6a8cbe/32.png) [@Wenqi\_Cheong](https://forum.ecmwf.int/u/Wenqi_Cheong)\ **Post date:** [26 May 2026 08:16 UTC](https://forum.ecmwf.int/t/extremely-high-value-of-era5-monthly-total-precipitation/15010/1 "2026-05-26T08:16:36Z")
Dear all, I’m confused when working on weather data for Kenya using ERA5 hourly data. I first computed monthly values myself from ERA5 hourly data following the method described in: [https://confluence.ecmwf.int/pages/viewpage.action?pageId=197702790](https://confluence.ecmwf.int/pages/viewpage.action?pageId=197702790) Specifically, I used ERA5 hourly total precipitation and aggregated it to monthly values using the recommended approach. After doing this, I found that some show surprisingly high monthly precipitation values, for example: `country year month lat lon tp_monthly_mm` `Kenya 2014 7 1.25 35.25 1179.508` `Kenya 2014 6 1.25 35.5 1436.107` `Kenya 2014 10 1.25 35.5 1039.039` `Kenya 2014 8 1.25 35.5 2039.74` `Kenya 2014 8 1.25 35.5 2039.74` This implies that some regions reach around 2000 mm in a single month, which is quite surprising to me. It feels extremely high. If this were annual precipitation, the magnitude would seem more reasonable, but as monthly totals I am unsure whether this is realistic for this region. To double-check, I also used ERA5 monthly data instead of aggregating hourly data myself. I perform the calculations in Stata: ```auto * Calculate monthly total precipitation by converting from daily values rename tp tp_perday * Create number of days in each month gen d = . replace d = 31 if inlist(month, 1, 3, 5, 7, 8, 10, 12) replace d = 30 if inlist(month, 4, 6, 9, 11) replace d = 28 if month == 2 * adjustment for February replace d = 29 if month == 2 & inlist(year, 2012, 2016, 2020) * Convert to monthly total precipitation (mm) gen tp = tp_perday * 1000 * d ``` The results are very similar to my hourly-based aggregation, which suggests that my calculation procedure is consistent. `country year month lat lon tp_monthly_mm tp` `Kenya 2014 7 1.25 35.25 1179.508 1179.6` `Kenya 2014 6 1.25 35.5 1436.107 1434.402` `Kenya 2014 10 1.25 35.5 1039.039 1038.994` `Kenya 2014 8 1.25 35.5 2039.74 2039.673` `Kenya 2014 8 1.25 35.5 2039.74 2039.673` However, I still have some concerns: 1. Does this mean that ERA5 total precipitation can realistically reach ~2000 mm/month in some locations in Kenya? 2. Or could these high values be related to known biases or characteristics of ERA5 precipitation? 3. I could not find any reports of extreme flooding events corresponding to such high values, so I am unsure whether this magnitude is climatologically reasonable. I would appreciate any clarification on whether this level of monthly precipitation is expected in ERA5 for East Africa, or whether there might be something I am missing in the interpretation of tp in either hourly or monthly datasets. Many thanks Wenqi ---
**Author:** ![Lyubomir\_Durankev](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/l/cab0a1/32.png) [@Lyubomir\_Durankev](https://forum.ecmwf.int/u/Lyubomir_Durankev)\ **Post date:** [10 June 2026 08:23 UTC](https://forum.ecmwf.int/t/extremely-high-value-of-era5-monthly-total-precipitation/15010/2 "2026-06-10T08:23:03Z")
Same here. I found the following explanation: The issue: The model calculates an average rainfall for that entire 30 × 30 km block. If a heavy, isolated thunderstorm only covers 10% of that area, ERA5 spreads that rainfall volume across the entire grid cell. The result: Your localized area gets a high hourly volume, even though the actual point measurement might have been much lower. ---
**Author:** ![Lyubomir\_Durankev](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/l/cab0a1/32.png) [@Lyubomir\_Durankev](https://forum.ecmwf.int/u/Lyubomir_Durankev)\ **Post date:** [10 June 2026 12:47 UTC](https://forum.ecmwf.int/t/extremely-high-value-of-era5-monthly-total-precipitation/15010/3 "2026-06-10T12:47:01Z")
Please ignore my previous answer. I was getting double the expected precipitation just because 00:00 belongs to the previous day, not to the next one. The next day’s readings actually start from 01:00. ---
**Author:** ![Lyubomir\_Durankev](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/l/cab0a1/32.png) [@Lyubomir\_Durankev](https://forum.ecmwf.int/u/Lyubomir_Durankev)\ **Post date:** [10 June 2026 12:57 UTC](https://forum.ecmwf.int/t/extremely-high-value-of-era5-monthly-total-precipitation/15010/4 "2026-06-10T12:57:55Z")
> [@Wenqi\_Cheong](#): > > [Conversion table for accumulated variables (total precipitation/fluxes) - Copernicus Knowledge Base - ECMWF Confluence Wiki](https://confluence.ecmwf.int/pages/viewpage.action?pageId=197702790) On more nuance here. The docs say “Total precipitation over the one hour ending at forecast step.” but this seems to apply for regular ERA5 hourly accumulated precipitation. For ERA5-Land, which I use, summing hourly values would overcount badly because each hour is cumulative from midnight.