Previous studies have reached different conclusions as to whether geomagnetic activity, or weather and weather changes are related to the risk of having or dying from an acute myocardial infarction (AMI). We linked the Northern Sweden MONICA AMI registry to databases on temperature, barometric pressure, relative humidity, the Arctic Oscillation (AO), and geomagnetic activity and found that a temperature rise increased the number of non-fatal AMIs, an increase in the AO increased fatal as well as non-fatal AMIs, but there was no relation between the geomagnetic activity and AMI incidence or case fatality.