July 1 (Reuters) - U.S. energy firms likely added an above normal 81 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 61 bcf during the same week a year ago and an average increase for that week of 64 bcf over the past five years (2021-2025).

In the prior week ended June 19, energy firms added 76 bcf of gas into storage. USOILN=ECI

If correct, the forecast for the week ended June 26 would increase stockpiles to 2.916 trillion cubic feet. That figure would be about 1% below the same week a year ago and about 6.2% 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 72 total degree days (TDDs) last week, lower than the 30-year normal of 75 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 12 analysts, whose estimates ranged from injections of 57 bcf to 90 bcf, with a median increase of 81 bcf.

Early estimates for the week ending July 3 ranged from injections of 14 bcf to 82 bcf, with an average increase of 52 bcf.

Those figures compare with an injection of 81 bcf during the same week last year and a five-year average increase of 51 bcf.

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