Skip to main content
SunnyDays

ERA5 almanac — 8 years of real data

Costa Rica — Guanacaste in April

Costa Rica — Guanacaste in April: 40% of days see measurable rain, 96°F average high, 33% of days historically clear (n=240, ERA5 2018–2025).

Costa Rica — Guanacaste in April is historically a poor month for sun: only 33% of days clear across 8 years (n=240, avg high 96°F). 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 April

Clear-sky percentage for Costa Rica — Guanacaste in April, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early April
1st–15th		 42% n=120 96°F
Late April
16th–end		 24% n=120 96°F
Full month average 33% n=240 96°F

Sunshine & warmth in April

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 April. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early April
1st–15th		 100% n=120
Late April
16th–end		 100% n=120
Full month average 100% n=240
11.6 h median sunshine per day 97% of days exceed 8 h sunshine 40% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 33%. Sunshine-based “warm & sunny”: 100%. The 67-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 mostly overcast in April historically: only 33% of days are clear across 8 years (n=240), avg high 96°F. Most visitors this month will see more clouds than sun.

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 ← this page 33% n=240 All destinations →
May 9% n=248 All destinations →
June 5% n=240 All destinations →
July 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 April?

Sometimes. Costa Rica — Guanacaste sees measurable rain on 40% of days in April historically (n=240 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Costa Rica — Guanacaste good for sun in April?

It's mixed. Costa Rica — Guanacaste in April is clear on 33% of days historically (avg high 96°F, n=240 days, ERA5 2018–2025) — the outcome varies year to year.

How Costa Rica — Guanacaste compares in April

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.

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.