June 17 (Reuters) - U.S. energy firms likely added a slightly above-normal 75 billion cubic feet of natural gas into storage last week, according to the average estimate in a Reuters poll released on Wednesday.

The estimate compares with an injection of 97 bcf during the same week a year ago and an average increase for that week of 73 bcf over the past five years (2021-2025).

In the prior week ended June 5, energy firms added 108 bcf of gas into storage. USOILN=ECI

If correct, the forecast for the week ended June 12 would increase stockpiles to 2.761 trillion cubic feet. That figure would be about 1% below the same week a year ago and about 5.9% above the five-year average for the week.

The U.S. Energy Information Administration is scheduled to release its weekly storage report at 10:30 a.m. EDT (1430 GMT) on Thursday.

There were 83 total degree days (TDDs) last week, higher than the 30-year normal of 69 TDDs for the period, data from financial firm LSEG showed.

Total degree days measure the number of degrees a day's average temperature is above or below 65 degrees Fahrenheit (18 degrees Celsius) to estimate demand to cool or heat homes and businesses.

Reuters polled 10 analysts, whose estimates ranged from injections of 67 bcf to 95 bcf, with a median increase of 74 bcf.

Early estimates for the week ending June 19 ranged from injections of 65 bcf to 96 bcf, with an average increase of 80 bcf.

Those figures compare with an injection of 96 bcf during the same week last year and a five-year average increase of 75 bcf.

Following is a list of poll participants. All figures are in billion cubic feet:

Organization	Forecasts in bcf
DTN	67
Energy Ventures Analysis	71
TFS Energy	72
Baker & O'Brien	73
Gelber & Associates	74
LSEG	74
Natural Gas Intelligence	74
SMC report	78
Schneider	81
C H Guernsey	95