The online tool will offer forecast information more frequently than public weather forecasts which would allow retailers and brands to develop weather and location-targeted short-period events that are not possible using general weather forecasts.
Currently brands tend to rely on historical climatological data to plan campaigns.
Retailers would be able to offer different voucher campaigns in Manchester and London if it is raining in one location and sunny in the other, for example.
It will also help retailers identify the most relevant channel to use to communicate with customers in different weather conditions, so that it can push online messaging in wet weather or mobile messaging in warmer weather.
The tool is due to launch later this year in partnership with affiliate network Trade Doubler. The Met Office has worked with the network to measure how weather affects online sales differently within different sectors.