ERA5 almanac — 8 years of real data

Costa Rica — Guanacaste in July

Costa Rica — Guanacaste in July: 63% of days see measurable rain, 88°F average high, 16% of days historically clear (n=248, ERA5 2018–2025).

Costa Rica — Guanacaste in July is historically a poor month for sun: only 16% of days clear across 8 years (n=248, avg high 88°F). February is the clearest month for Costa Rica — Guanacaste historically. Historical average, not a forecast.

What you are reading: 8-year historical averages from the ERA5 reanalysis, not a forecast. A month that is historically 90% clear can still be overcast on your specific trip. For this week’s actual forecast, see the live Costa Rica — Guanacaste page. Both can be true at once: “historically strong in this month; this particular week is not.” We label which is which.

Early vs. Late July

Clear-sky percentage for Costa Rica — Guanacaste in July, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period	% Clear days	Sample (n)	Avg high
Early July 1st–15th	9%	n=120	88°F
Late July 16th–end	23%	n=128	88°F
Full month average	16%	n=248	88°F

Sunshine & warmth in July

A second measure using actual sunshine hours (ERA5 sunshine_duration), not the daily weather code. A Lowcountry day with 12 hours of sun and a 25-minute afternoon storm is counted below as a warm, sunny day — because it was. How we define this.

Sunshine-based metrics for Costa Rica — Guanacaste in July. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period	Warm & sunny (≥72°F, >6 h sun)	Sample (n)
Early July 1st–15th	90%	n=120
Late July 16th–end	95%	n=128
Full month average	93%	n=248

9.6 h median sunshine per day 74% of days exceed 8 h sunshine 63% of days see ≥ 1 mm rain — rain is not hidden

Comparison (old vs new): WMO-code “clear” bar: 16%. Sunshine-based “warm & sunny”: 93%. The 77-point gap is from brief afternoon convective storms that stamp the whole day as “rain” in the WMO code but leave the bulk of the sunshine untouched.

Bottom line

Costa Rica — Guanacaste is a poor choice for sun in July: just 16% of days clear historically (n=248). February is the historically strongest month for sun here. The 8-year record is consistent — this is not a fluke bad stretch.

→ See all destinations in February — historically the best month for sun in Costa Rica — Guanacaste.

Every month in Costa Rica — Guanacaste

Compare across all months with data. Numbers are historical clear-sky %.

Historical clear-sky % for Costa Rica — Guanacaste, all months, ERA5 2018–2025.
Month	% Clear	Sample (n)
January	79%	n=248	All destinations →
February	84%	n=226	All destinations →
March	70%	n=248	All destinations →
April	33%	n=240	All destinations →
May	9%	n=248	All destinations →
June	5%	n=240	All destinations →
July ← this page	16%	n=248	All destinations →
August	6%	n=248	All destinations →
September	2%	n=240	All destinations →
October	2%	n=248	All destinations →
November	18%	n=240	All destinations →
December	62%	n=248	All destinations →

Frequently asked

Does it rain in Costa Rica — Guanacaste in July?

Yes, frequently. In Costa Rica — Guanacaste, 63% of days in July see measurable rain, based on 8 years of ERA5 historical data (n=248 days, 2018–2025). This is a historical average, not a forecast.

Is Costa Rica — Guanacaste good for sun in July?

Not usually. Costa Rica — Guanacaste is historically overcast in July: only 16% of days are clear (avg high 88°F, n=248 days, ERA5 2018–2025). February is historically far better for sun here.

How Costa Rica — Guanacaste compares in July

Head-to-head clear-sky comparisons against destinations travelers plausibly weigh against Costa Rica — Guanacaste this month — same passport tier, similar flight distance, both sides from the same 8-year ERA5 record.

→ Costa Rica — Guanacaste vs Punta Mita in July — Punta Mita is 16% clear historically
→ Costa Rica — Guanacaste vs Wilmington in July — Wilmington is 16% clear historically
→ Costa Rica — Guanacaste vs Atlanta in July — Atlanta is 15% clear historically

→ Costa Rica — Guanacaste live forecast — this week’s actual 7-day weather, not historical
→ Best destinations in July — all destinations ranked by July clear-sky %
→ All destinations
→ Raw data (JSON) — buckets, n, source

All percentages are historical averages from the ERA5 reanalysis via Open-Meteo, 8 full years (2018–2025). “Clear” means avg high ≥ 72 °F, precipitation < 1 mm, and a non-precipitation weather code. This is history, not a forecast. The live 7-day outlook for any destination is on its own page and may differ from the long-run average. Data from Open-Meteo.