* Summer gas season begins
* Weather outlook warmer for weekend, most of next week
LONDON, April 1 (Reuters) - British wholesale gas prices were mostly down on Friday at the start of the new summer gas season, as milder weather forecasts for the weekend and next week lowered gas demand for heating.
Gas for day-ahead delivery was down 0.83 pence at 28.55 pence per therm at 0749 GMT from the previous settlement, while gas for weekend delivery was 0.55 pence lower at 28.45 p/therm.
Gas for immediate delivery, bucked the trend and was 0.30 pence higher at 28.70 pence per therm.
Temperatures will be higher than average at the weekend and for most of next week, lowering demand for gas for heating, before turning cooler.
The summer gas season started on Friday which will run until October. This is usually a period of lower demand for gas due to warmer temperatures and when gas is injected into storage.
Supply from the UK Continental Shelf and Norway was healthy, however.
In the Dutch market, May gas prices at the TTF hub declined by 0.21 euros to 11.77 euros per megawatt hour.
In the European carbon market, benchmark EU allowances inched down by 0.03 euros to 5.19 euros a tonne.
The European Commission is due to release preliminary data on the EU Emissions Trading System's emissions for 2015 at 1000 GMT (1200 CET). (Reporting by Nina Chestney, editing by Nerijus Adomaitis)