“Payment Pulse” deals with the hearth-wrenching reality of Southern California homebuying finances — it’s really about the size of the monthly check to the lender, not the enormity of price tag.

Buzz: A typical Southern California homebuyer in March landed a house payment almost one-third higher than a year ago.

Source: My trusty spreadsheet looked at what’s become a blood-boiling mix: the intersection of higher home prices (monthly median from DQNews) and rising mortgage rates (average 30-year deals from Freddie Mac) that generate a hypothetical yet typical monthly home loan payment a buyer would get, assuming a 20% downpayment. Note: We do not account for property taxes, association dues or insurance.

Rate watch: 3.79% three-month average vs. 3.44% the previous month and 2.88% a year earlier. What does the do to a borrower’s buying power? In one month, it’s down 4.3% and down 10.9% in a year — a drop larger than 96% of all 12-month periods since 1988.

Pay to the order of …

In the six-county region, last month’s buyer got a record-high $2,738 house payment for the record median home price of $735,000.

The estimated payment is 8.8% higher just in a month. And over a year, it’s up 31% or a $646 a month payment jump heading to the lender. The median by itself is up 17% over 12 months.

Do not forget that this math assumes a $147,000 downpayment — that’s 20% — a financial burden that’s grown by $21,000 in a year.

Locally speaking

My spreadsheet found the same payment trends within each of the counties …

Los Angeles: Record-high $3,129 payment on the record $840,000 median. Payment change: 26% in a year, or $639 a month. The median price was up 12% over 12 months. The 20% downpayment was $168,000 — up $18,000 in a year.

Orange: Record-high $3,799 payment on the record $1,020,000 median. The loan payment was up 37% in a year, or $1,027 a month. The median home price was up 22% over 12 months. And the downpayment was $204,000 — up $37,000 in a year.

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Riverside: $2,160 payment on the record $580,000 median. That payment was flat compared with the all-time high. The loan payment was up 36% in a year, or $577 a month. The median home price was up 22% over 12 months. Downpayment was up $116,000 — or $20,600 in a year.

San Bernardino: $1,844 payment on the record $495,000 median. That payment was 2% below the all-time high. The loan payment was up 29% in a year or $416 a month. The median price was up 15% over 12 months, and the downpayment was $99,000, up $13,000 in a year.

San Diego: Record-high $2,998 payment on the record $805,000 median. The loan payment was up 33% in a year or $697 a month. The median home price was up 19% over 12 months, and the downpayment was $161,000, up $25,400 in a year.

Ventura: $2,887 payment on the record $775,000 median. That payment is 10% below the all-time high. The loan payment was up 32% in a year or $646 a month. The median price was up 18% over 12 months, and the downpayment was $155,000, up $23,100 in a year.

Bottom line

Rarely have prices and rates put pressure more swiftly on house hunters.

Ponder these soaring costs in a historical context. Regionally, the year’s estimated house payment jump tops 96% of all 12-month periods since 1988.

And by county? Los Angeles (93%), Orange (96%), Riverside (96%), San Bernardino (92%), San Diego (95%), and Ventura (94%).

Jonathan Lansner is the business columnist for the Southern California News Group. He can be reached at [email protected]