Accepted Article A 19 th century daily surface pressure series for the Southwestern Cape region of South Africa: 1834-1899 Jessica Picas¹, Stefan Grab¹ and Rob Allan² 1. School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg, South Africa 2. Hadley Centre, Met Office, Exeter, Devon, United Kingdom *Correspondence: J.A. Picas, University of the Witwatersrand, Johannesburg, South Africa. E mail: picasj5@gmail.com. This article was funded by a grant from National Research Foundation (NRF) of South Africa, through the ACCESS programme. Rob Allan is supported by funding from the Joint BEIS/Defra Met Office Hadley Centre Climate Programme (GA01101). Abstract The first daily mean sea-level pressure (MSLP) series for the Southwestern Cape region of South Africa is presented for the 19 th century, and is one of the longest and oldest for the southern hemisphere. Sub-daily barometer readings from the South African Astronomical Observatory were digitized, together with temperature readings, and extend over the period 1834-1899. Pressure readings were recorded using mercury barometers and so needed to be corrected and reduced to standard conditions. Overall, austral winter (June, July, August) has the highest mean monthly MSLP values, symptomatic of the ridging anticyclones during this season. The year 1862 stands out with particularly low MSLP values and has 27 days during austral winter that were below the 10 th percentile. This most likely indicates that the winter of 1862 experienced the highest number of passing cold fronts throughout the 66 year study period. KEY WORDS: barometer observations, MSLP data, South African Astronomical Observatory, historical climatology This article is protected by copyright. All rights reserved. This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/joc.5890