The soil resistivity data is the key factor in designing a grounding system for a specific performance objective. All soil conducts electrical current, with some soils having good electrical conductivity while the majority has poor electrical conductivity. The soil resistivity varies widely throughout the whole territory of Latvia and changes dramatically within small areas. Factors that affect the soil resistivity may be summarised as: type of the ground, stratification; layers of different types of soil, moisture content, temperature; the ground resistivity is lower in summer and higher in winter, chemical composition, topography; rugged topography has a similar effect on the resistivity measurement as the local surface resistivity variation caused by weathering and moisture. Factors such as maximum probe depths, lengths of cables required, efficiency of the measuring technique, cost (determined by the time and the size of the survey crew) and ease of interpretation of the data need to be considered, when selecting the test type. It has been demonstrated that the effects of geological and seasonal variations in soils have a considerable impact on the electrical characteristics and therefore can affect grounding system performance. It has also been demonstrated that a multi-disciplinary approach to grounding should benefit the subject. Certainly here are aspects of geophysics and geology that would usefully complement the traditional purely electrical engineering approach. What is somewhat disappointing is that effects of weather and geology have for so long been ignored. Perhaps it can be shown that under all combinations of such conditions the effects on measurements and performance are negligible. If this is indeed the case, well and good, it will maintain the resent simplicity of approach. However, in order to be able to confidently disregard such effects, their magnitudes must first be properly quantified and so far this does not appear to have been adequately done.